Schema

Agent

Defines the interface that all ACP-compliant agents must implement. Agents are programs that use generative AI to autonomously modify code. They handle requests from clients and execute tasks using language models and tools.

authenticate

Authenticates the client using the specified authentication method. Called when the agent requires authentication before allowing session creation. The client provides an authentication method ID that was advertised during initialization and whose type defines the authenticate flow. After successful authentication, the client can proceed to create sessions with session/new without receiving an auth_required (-32000) error. See protocol docs: Initialization

AuthenticateRequest

Request parameters for the authenticate method. Specifies which authentication method to use. Type: Object Properties:

AuthenticateResponse

Response to the authenticate method. Type: Object Properties:

initialize

Establishes the connection with a client and negotiates protocol capabilities. This method is called once at the beginning of the connection to:

• Negotiate the protocol version to use
• Exchange capability information between client and agent
• Determine available authentication methods

The agent should respond with its supported protocol version and capabilities. See protocol docs: Initialization

InitializeRequest

Request parameters for the initialize method. Sent by the client to establish connection and negotiate capabilities. See protocol docs: Initialization Type: Object Properties:

InitializeResponse

Response to the initialize method. Contains the negotiated protocol version and agent capabilities. See protocol docs: Initialization Type: Object Properties:

logout

Logs out of the current authenticated state. After a successful logout, all new sessions will require authentication. There is no guarantee about the behavior of already running sessions.

LogoutRequest

Request parameters for the logout method. Terminates the current authenticated session. Type: Object Properties:

LogoutResponse

Response to the logout method. Type: Object Properties:

session/cancel

Cancels ongoing operations for a session. This is a notification sent by the client to cancel an ongoing prompt turn. Upon receiving this notification, the Agent SHOULD:

• Stop all language model requests as soon as possible
• Abort all tool call invocations in progress
• Send any pending session/update notifications
• Respond to the original session/prompt request with the cancelled stop reason

See protocol docs: Cancellation

CancelNotification

Notification to cancel ongoing operations for a session. See protocol docs: Cancellation Type: Object Properties:

session/close

Closes an active session and frees up any resources associated with it. This method is only available if the agent advertises the sessionCapabilities.close capability. The agent must cancel any ongoing work (as if session/cancel was called) and then free up any resources associated with the session.

CloseSessionRequest

Request parameters for closing an active session. If supported, the agent must cancel any ongoing work related to the session (treat it as if session/cancel was called) and then free up any resources associated with the session. Only available if the Agent supports the sessionCapabilities.close capability. Type: Object Properties:

CloseSessionResponse

Response from closing a session. Type: Object Properties:

session/delete

Deletes an existing session from session/list. This method is only available if the agent advertises the sessionCapabilities.delete capability.

DeleteSessionRequest

Request parameters for deleting an existing session from session/list. Only available if the Agent supports the sessionCapabilities.delete capability. Type: Object Properties:

DeleteSessionResponse

Response from deleting a session. Type: Object Properties:

session/list

Lists existing sessions known to the agent. This method is only available if the agent advertises the sessionCapabilities.list capability. The agent should return metadata about sessions with optional filtering and pagination support.

ListSessionsRequest

Request parameters for listing existing sessions. Only available if the Agent supports the sessionCapabilities.list capability. Type: Object Properties:

ListSessionsResponse

Response from listing sessions. Type: Object Properties:

session/load

Loads an existing session to resume a previous conversation. This method is only available if the agent advertises the loadSession capability. The agent should:

• Restore the session context and conversation history
• Connect to the specified MCP servers
• Stream the entire conversation history back to the client via notifications

See protocol docs: Loading Sessions

LoadSessionRequest

Request parameters for loading an existing session. Only available if the Agent supports the loadSession capability. See protocol docs: Loading Sessions Type: Object Properties:

LoadSessionResponse

Response from loading an existing session. Type: Object Properties:

session/new

Creates a new conversation session with the agent. Sessions represent independent conversation contexts with their own history and state. The agent should:

• Create a new session context
• Connect to any specified MCP servers
• Return a unique session ID for future requests

May return an auth_required (-32000) error if the agent requires authentication. See protocol docs: Session Setup

NewSessionRequest

Request parameters for creating a new session. See protocol docs: Creating a Session Type: Object Properties:

NewSessionResponse

Response from creating a new session. See protocol docs: Creating a Session Type: Object Properties:

session/prompt

Processes a user prompt within a session. This method handles the whole lifecycle of a prompt:

• Receives user messages with optional context (files, images, etc.)
• Processes the prompt using language models
• Reports language model content and tool calls to the Clients
• Requests permission to run tools
• Executes any requested tool calls
• Returns when the turn is complete with a stop reason

See protocol docs: Prompt Turn

PromptRequest

Request parameters for sending a user prompt to the agent. Contains the user’s message and any additional context. See protocol docs: User Message Type: Object Properties:

PromptResponse

Response from processing a user prompt. See protocol docs: Check for Completion Type: Object Properties:

session/resume

Resumes an existing session without returning previous messages. This method is only available if the agent advertises the sessionCapabilities.resume capability. The agent should resume the session context, allowing the conversation to continue without replaying the message history (unlike session/load).

ResumeSessionRequest

Request parameters for resuming an existing session. Resumes an existing session without returning previous messages (unlike session/load). This is useful for agents that can resume sessions but don’t implement full session loading. Only available if the Agent supports the sessionCapabilities.resume capability. Type: Object Properties:

ResumeSessionResponse

Response from resuming an existing session. Type: Object Properties:

session/set_config_option

Sets the current value for a session configuration option.

SetSessionConfigOptionRequest

Request parameters for setting a session configuration option. Type: Union Shared properties: Variants:

SetSessionConfigOptionResponse

Response to session/set_config_option method. Type: Object Properties:

session/set_mode

Sets the current mode for a session. Allows switching between different agent modes (e.g., “ask”, “architect”, “code”) that affect system prompts, tool availability, and permission behaviors. The mode must be one of the modes advertised in availableModes during session creation or loading. Agents may also change modes autonomously and notify the client via current_mode_update notifications. This method can be called at any time during a session, whether the Agent is idle or actively generating a response. See protocol docs: Session Modes

SetSessionModeRequest

Request parameters for setting a session mode. Type: Object Properties:

SetSessionModeResponse

Response to session/set_mode method. Type: Object Properties:

Client

Defines the interface that ACP-compliant clients must implement. Clients are typically code editors (IDEs, text editors) that provide the interface between users and AI agents. They manage the environment, handle user interactions, and control access to resources.

elicitation/complete

Notification that a URL-based elicitation has completed. See protocol docs: Elicitation

CompleteElicitationNotification

Notification sent by the agent when a URL-based elicitation is complete. Type: Object Properties:

elicitation/create

Requests structured user input via a form or URL. See protocol docs: Elicitation

CreateElicitationRequest

Request from the agent to elicit structured user input. The agent sends this to the client to request information from the user, either via a form or by directing them to a URL. Elicitations are tied to a session (optionally a tool call) or a request. Type: Union Shared properties: Variants:

CreateElicitationResponse

Response from the client to an elicitation request. Type: Union Shared properties: Variants:

fs/read_text_file

Reads content from a text file in the client’s file system. Only available if the client advertises the fs.readTextFile capability. Allows the agent to access file contents within the client’s environment. See protocol docs: Client

ReadTextFileRequest

Request to read content from a text file. Only available if the client supports the fs.readTextFile capability. Type: Object Properties:

ReadTextFileResponse

Response containing the contents of a text file. Type: Object Properties:

fs/write_text_file

Writes content to a text file in the client’s file system. Only available if the client advertises the fs.writeTextFile capability. Allows the agent to create or modify files within the client’s environment. See protocol docs: Client

WriteTextFileRequest

Request to write content to a text file. Only available if the client supports the fs.writeTextFile capability. Type: Object Properties:

WriteTextFileResponse

Response to fs/write_text_file Type: Object Properties:

session/request_permission

Requests permission from the user for a tool call operation. Called by the agent when it needs user authorization before executing a potentially sensitive operation. The client should present the options to the user and return their decision. If the client cancels the prompt turn via session/cancel, it MUST respond to this request with the cancelled outcome. See protocol docs: Requesting Permission

RequestPermissionRequest

Request for user permission to execute a tool call. Sent when the agent needs authorization before performing a sensitive operation. See protocol docs: Requesting Permission Type: Object Properties:

RequestPermissionResponse

Response to a permission request. Type: Object Properties:

session/update

Handles session update notifications from the agent. This is a notification endpoint (no response expected) that receives real-time updates about session progress, including message chunks, tool calls, and execution plans. Note: Clients SHOULD continue accepting tool call updates even after sending a session/cancel notification, as the agent may send final updates before responding with the cancelled stop reason. See protocol docs: Agent Reports Output

SessionNotification

Notification containing a session update from the agent. Used to stream real-time progress and results during prompt processing. See protocol docs: Agent Reports Output Type: Object Properties:

terminal/create

Executes a command in a new terminal Only available if the terminal Client capability is set to true. Returns a TerminalId that can be used with other terminal methods to get the current output, wait for exit, and kill the command. The TerminalId can also be used to embed the terminal in a tool call by using terminal tool call content. The Agent is responsible for releasing the terminal by using the terminal/release method. See protocol docs: Terminals

CreateTerminalRequest

Request to create a new terminal and execute a command. Type: Object Properties:

CreateTerminalResponse

Response containing the ID of the created terminal. Type: Object Properties:

terminal/kill

Kills the terminal command without releasing the terminal While terminal/release will also kill the command, this method will keep the TerminalId valid so it can be used with other methods. This method can be helpful when implementing command timeouts which terminate the command as soon as elapsed, and then get the final output so it can be sent to the model. Note: Call terminal/release when TerminalId is no longer needed. See protocol docs: Terminals

KillTerminalRequest

Request to kill a terminal without releasing it. Type: Object Properties:

KillTerminalResponse

Response to terminal/kill method Type: Object Properties:

terminal/output

Gets the terminal output and exit status Returns the current content in the terminal without waiting for the command to exit. If the command has already exited, the exit status is included. See protocol docs: Terminals

TerminalOutputRequest

Request to get the current output and status of a terminal. Type: Object Properties:

TerminalOutputResponse

Response containing the terminal output and exit status. Type: Object Properties:

terminal/release

Releases a terminal The command is killed if it hasn’t exited yet. Use terminal/wait_for_exit to wait for the command to exit before releasing the terminal. After release, the TerminalId can no longer be used with other terminal/* methods, but tool calls that already contain it, continue to display its output. The terminal/kill method can be used to terminate the command without releasing the terminal, allowing the Agent to call terminal/output and other methods. See protocol docs: Terminals

ReleaseTerminalRequest

Request to release a terminal and free its resources. Type: Object Properties:

ReleaseTerminalResponse

Response to terminal/release method Type: Object Properties:

terminal/wait_for_exit

Waits for the terminal command to exit and return its exit status See protocol docs: Terminals

WaitForTerminalExitRequest

Request to wait for a terminal command to exit. Type: Object Properties:

WaitForTerminalExitResponse

Response containing the exit status of a terminal command. Type: Object Properties:

Protocol Level

Defines the interface that ACP-compliant agents and clients must both implement. Notifications whose methods start with ‘$/' are messages which are protocol implementation dependent and might not be implementable in all clients or agents. For example if the implementation uses a single threaded synchronous programming language then there is little it can do to react to a `$/cancel_request` notification. If an agent or client receives notifications starting with ’$/’ it is free to ignore the notification.

$/cancel_request

Cancels an ongoing request. This is a notification sent by the side that sent a request to cancel that request. Upon receiving this notification, the receiver:

1. MAY cancel the corresponding request activity and all nested activities
2. MAY send any pending notifications.
3. MUST send one of these responses for the original request:

• Valid response with appropriate data (partial results or cancellation marker)
• Error response with code -32800 (Cancelled)

See protocol docs: Cancellation

CancelRequestNotification

Notification to cancel an ongoing request. See protocol docs: Cancellation Type: Object Properties:

AgentAuthCapabilities

Authentication-related capabilities supported by the agent. Type: Object Properties:

AgentCapabilities

Capabilities supported by the agent. Advertised during initialization to inform the client about available features and content types. See protocol docs: Agent Capabilities Type: Object Properties:

Annotations

Optional annotations for the client. The client can use annotations to inform how objects are used or displayed Type: Object Properties:

AudioContent

Audio provided to or from an LLM. Type: Object Properties:

AuthCapabilities

Authentication capabilities supported by the client. Advertised during initialization to inform the agent which authentication method types the client can handle. This governs opt-in types that require additional client-side support. Type: Object Properties:

AuthMethod

Describes an available authentication method. The type field acts as the discriminator in the serialized JSON form. When no type is present, the method is treated as agent. Type: Union

AuthMethodAgent

Agent handles authentication itself through authenticate. This is the default authentication method type. Type: Object Properties:

AuthMethodId

Typed identifier used for auth method values on the wire. Type: string

AuthMethodTerminal

Terminal-based authentication method. The client runs the configured agent program as a separate interactive process for the user to authenticate via a TUI. Agents MUST advertise this method only when the client enabled its terminal authentication capability. A zero exit status signals success. Any other termination signals failure. The client MUST NOT pass this method to authenticate. Type: Object Properties:

AvailableCommand

Information about a command. Type: Object Properties:

AvailableCommandInput

The input specification for a command. All text that was typed after the command name is provided as input. Type: Object Properties:

AvailableCommandsUpdate

Available commands are ready or have changed Type: Object Properties:

BlobResourceContents

Binary resource contents. Type: Object Properties:

BooleanConfigOptionCapabilities

Capabilities for boolean session configuration options. Supplying \{\} means the client supports boolean session configuration options. Type: Object Properties:

BooleanPropertySchema

Schema for boolean properties in an elicitation form. Type: Object Properties:

ClientCapabilities

Capabilities supported by the client. Advertised during initialization to inform the agent about available features and methods. See protocol docs: Client Capabilities Type: Object Properties:

ClientSessionCapabilities

Session-related capabilities supported by the client. Type: Object Properties:

CompactionCapabilities

Client support for ID-addressed context compaction updates. Type: object

CompactionId

Unique identifier for a context compaction within a session. Type: string

CompactionStatus

Lifecycle state of a context compaction. Type: Union

CompactionSummaryChunk

A content block appended to a compaction’s summary. A first-seen ID creates an in-progress compaction. Chunks append in receive order. Agents MUST only send this update when the Client advertised the session.compaction Client capability. Type: Object Properties:

CompactionUpdate

A context compaction upsert. The first notification fixes the compaction’s timeline position. Later updates with the same ID patch that entity in place. Agents MUST only send this update when the Client advertised the session.compaction Client capability. summary, error, and _meta have patch semantics: omission leaves the stored value unchanged, null clears it, and a concrete value replaces it. summary: [] also clears the summary. Type: Object Properties:

ConfigOptionUpdate

Session configuration options have been updated. Type: Object Properties:

Content

Standard content block (text, images, resources). Type: Object Properties:

ContentBlock

Content blocks represent displayable information in the Agent Client Protocol. Content blocks appear in:

• User prompts sent via session/prompt
• Language model output streamed through session/update notifications
• Progress updates and results from tool calls

This structure is compatible with the Model Context Protocol (MCP), so agents can forward content from MCP tool outputs without transformation. See protocol docs: Content Type: Union

ContentChunk

A streamed item of content Type: Object Properties:

Cost

Cost information for a session. Type: Object Properties:

CurrentModeUpdate

The current mode of the session has changed See protocol docs: Session Modes Type: Object Properties:

Diff

A diff representing file modifications. Shows changes to files in a format suitable for display in the client UI. See protocol docs: Content Type: Object Properties:

ElicitationAcceptAction

The user accepted the elicitation and provided content. Type: Object Properties:

ElicitationCapabilities

Elicitation capabilities supported by the client. Type: Object Properties:

ElicitationContentValue

Allowed wire representations for ElicitationContentValue. Type: Union

ElicitationFormCapabilities

Form-based elicitation capabilities. Supplying \{\} means the client supports form-based elicitation. Type: Object Properties:

ElicitationFormMode

Form-based elicitation mode where the client renders a form from the provided schema. Type: Union Shared properties: Variants:

ElicitationId

Unique identifier for an elicitation. Type: string

ElicitationPropertySchema

Property schema for elicitation form fields. Each variant corresponds to a JSON Schema "type" value. Single-select enums use type: "string" with enum or oneOf set. Multi-select enums use type: "array". Type: Union

ElicitationRequestScope

Request-scoped elicitation, tied to a specific JSON-RPC request outside of a session (e.g., during auth/configuration phases before any session is started). Type: Object Properties:

ElicitationSchema

Type-safe elicitation schema for requesting structured user input. This represents a JSON Schema object with primitive-typed properties, as required by the elicitation specification. Type: Object Properties:

ElicitationSchemaType

Type discriminator for elicitation schemas. Type: Union

ElicitationSessionScope

Session-scoped elicitation, optionally tied to a specific tool call. When toolCallId is set, the elicitation is tied to a specific tool call. This is useful when an agent receives an elicitation from an MCP server during a tool call and needs to redirect it to the user. Type: Object Properties:

ElicitationUrlCapabilities

URL-based elicitation capabilities. Supplying \{\} means the client supports URL-based elicitation. Type: Object Properties:

ElicitationUrlMode

URL-based elicitation mode where the client directs the user to a URL. Type: Union Shared properties: Variants:

EmbeddedResource

The contents of a resource, embedded into a prompt or tool call result. Type: Object Properties:

EmbeddedResourceResource

Resource content that can be embedded in a message. Type: Union

EnumOption

A titled enum option with a const value, human-readable title, and optional description. Type: Object Properties:

EnvVariable

An environment variable to set when launching an MCP server. Type: Object Properties:

Error

JSON-RPC error object. Represents an error that occurred during method execution, following the JSON-RPC 2.0 error object specification with optional additional data. See protocol docs: JSON-RPC Error Object Type: Object Properties:

ErrorCode

Predefined error codes for common JSON-RPC and ACP-specific errors. Standard errors use the JSON-RPC 2.0 codes. ACP-specific errors use the JSON-RPC server-error range (-32000 to -32099), and request cancellation uses -32800 from the range LSP reserves (-32899 to -32800). Type: Union

ExtNotification

Allows either side to send an arbitrary notification that is not part of the ACP spec. Extension notifications provide a way to send one-way messages for custom functionality while maintaining protocol compatibility. See protocol docs: Extensibility

ExtRequest

Allows for sending an arbitrary request that is not part of the ACP spec. Extension methods provide a way to add custom functionality while maintaining protocol compatibility. See protocol docs: Extensibility

ExtResponse

Allows for sending an arbitrary response to an extension request that is not part of the ACP spec. Extension methods provide a way to add custom functionality while maintaining protocol compatibility. See protocol docs: Extensibility

FileSystemCapabilities

File system capabilities that a client may support. See protocol docs: FileSystem Type: Object Properties:

HttpHeader

An HTTP header to set when making requests to the MCP server. Type: Object Properties:

ImageContent

An image provided to or from an LLM. Type: Object Properties:

Implementation

Metadata about the implementation of the client or agent. Describes the name and version of an ACP implementation, with an optional title for UI representation. Type: Object Properties:

IntegerPropertySchema

Schema for integer properties in an elicitation form. Type: Object Properties:

LogoutCapabilities

Logout capabilities supported by the agent. Supplying \{\} means the agent supports the logout method. Type: Object Properties:

McpCapabilities

MCP capabilities supported by the agent Type: Object Properties:

McpServer

Configuration for connecting to an MCP (Model Context Protocol) server. MCP servers provide tools and context that the agent can use when processing prompts. See protocol docs: MCP Servers Type: Union

McpServerHttp

HTTP transport configuration for MCP. Type: Object Properties:

McpServerSse

SSE transport configuration for MCP. Type: Object Properties:

McpServerStdio

Stdio transport configuration for MCP. Type: Object Properties:

MessageId

Unique identifier for a message within a session. Type: string

MultiSelectItems

Items for a multi-select (array) property schema. Type: Union

MultiSelectPropertySchema

Schema for multi-select (array) properties in an elicitation form. Type: Object Properties:

Notice

Fire-and-forget information for the user. Notices are live events rather than session history. Agents must not rely on a notice being received, displayed, or seen by the user. Agents MUST only send notices when the Client advertised the session.notices Client capability. Otherwise, Agents may use an agent message when the information should still be surfaced to the user. See RFD: Session Notices Type: Object Properties:

NoticeCapabilities

Client support for presenting live notices to the user. Type: object

NoticeSeverity

Severity hint for a session notice. Type: Union

NumberPropertySchema

Schema for number (floating-point) properties in an elicitation form. Type: Object Properties:

PermissionOption

An option presented to the user when requesting permission. Type: Object Properties:

PermissionOptionId

Unique identifier for a permission option. Type: string

PermissionOptionKind

The type of permission option being presented to the user. Helps clients choose appropriate icons and UI treatment. Type: Union

Plan

An execution plan for accomplishing complex tasks. Plans consist of multiple entries representing individual tasks or goals. Agents report plans to clients to provide visibility into their execution strategy. Plans can evolve during execution as the agent discovers new requirements or completes tasks. See protocol docs: Agent Plan Type: Object Properties:

PlanEntry

A single entry in the execution plan. Represents a task or goal that the assistant intends to accomplish as part of fulfilling the user’s request. See protocol docs: Plan Entries Type: Object Properties:

PlanEntryPriority

Priority levels for plan entries. Used to indicate the relative importance or urgency of different tasks in the execution plan. See protocol docs: Plan Entries Type: Union

PlanEntryStatus

Status of a plan entry in the execution flow. Tracks the lifecycle of each task from planning through completion. See protocol docs: Plan Entries Type: Union

PromptCapabilities

Prompt capabilities supported by the agent in session/prompt requests. Baseline agent functionality requires support for text and resource_link content blocks in prompt requests. Other variants must be explicitly opted in to. Capabilities for different types of content in prompt requests. Indicates which content types beyond the baseline (text and resource links) the agent can process. See protocol docs: Prompt Capabilities Type: Object Properties:

ProtocolVersion

Protocol version identifier. This version is only bumped for breaking changes. Non-breaking changes should be introduced via capabilities. Type: integer (uint16)

RequestId

JSON RPC Request Id An identifier established by the Client that MUST contain a String, Number, or NULL value if included. If it is not included it is assumed to be a notification. The value SHOULD normally not be Null [1] and Numbers SHOULD NOT contain fractional parts [2] The Server MUST reply with the same value in the Response object if included. This member is used to correlate the context between the two objects. [1] The use of Null as a value for the id member in a Request object is discouraged, because this specification uses a value of Null for Responses with an unknown id. Also, because JSON-RPC 1.0 uses an id value of Null for Notifications this could cause confusion in handling. [2] Fractional parts may be problematic, since many decimal fractions cannot be represented exactly as binary fractions. Type: Union

RequestPermissionOutcome

The outcome of a permission request. Type: Union

ResourceLink

A resource that the server is capable of reading, included in a prompt or tool call result. Type: Object Properties:

Role

The sender or recipient of messages and data in a conversation. Type: Union

SelectedPermissionOutcome

The user selected one of the provided options. Type: Object Properties:

SessionAdditionalDirectoriesCapabilities

Capabilities for additional session directories support. Supplying \{\} means the agent supports the additionalDirectories field on supported session lifecycle requests. Agents that also support session/list may return SessionInfo.additionalDirectories to report the complete ordered additional-root list associated with a listed session. Type: Object Properties:

SessionCapabilities

Session capabilities supported by the agent. As a baseline, all Agents MUST support session/new, session/prompt, session/cancel, and session/update. Optionally, they MAY support other session methods and notifications by specifying additional capabilities. Note: session/load is still handled by the top-level loadSession capability. This will be unified in future versions of the protocol. See protocol docs: Session Capabilities Type: Object Properties:

SessionCloseCapabilities

Capabilities for the session/close method. Supplying \{\} means the agent supports closing sessions. Type: Object Properties:

SessionConfigBoolean

A boolean on/off toggle session configuration option payload. Type: Object Properties:

SessionConfigGroupId

Unique identifier for a session configuration option value group. Type: string

SessionConfigId

Unique identifier for a session configuration option. Type: string

SessionConfigOption

A session configuration option selector and its current state. Type: Union Shared properties: Variants:

SessionConfigOptionCategory

Semantic category for a session configuration option. This is intended to help Clients distinguish broadly common selectors (e.g. model selector vs session mode selector vs thought/reasoning level) for UX purposes (keyboard shortcuts, icons, placement). It MUST NOT be required for correctness. Clients MUST handle missing or unknown categories gracefully. Category names beginning with _ are free for custom use, like other ACP extension methods. Category names that do not begin with _ are reserved for the ACP spec. Type: Union

SessionConfigOptionsCapabilities

Session configuration option capabilities supported by the client. Type: Object Properties:

SessionConfigSelect

A single-value selector (dropdown) session configuration option payload. Type: Object Properties:

SessionConfigSelectGroup

A group of possible values for a session configuration option. Type: Object Properties:

SessionConfigSelectOption

A possible value for a session configuration option. Type: Object Properties:

SessionConfigSelectOptions

Possible values for a session configuration option. Type: Union

SessionConfigValueId

Unique identifier for a session configuration option value. Type: string

SessionDeleteCapabilities

Capabilities for the session/delete method. Supplying \{\} means the agent supports deleting sessions from session/list. Type: Object Properties:

SessionId

A unique identifier for a conversation session between a client and agent. Each session has its own context, conversation history, and state, so one agent can run several independent sessions. See protocol docs: Session ID Type: string

SessionInfo

Information about a session returned by session/list Type: Object Properties:

SessionInfoUpdate

Update to session metadata. All fields are optional to support partial updates. Agents send this notification to update session information like title or custom metadata. Clients can use it to keep session titles and state current. Type: Object Properties:

SessionListCapabilities

Capabilities for the session/list method. Supplying \{\} means the agent supports listing sessions. Type: Object Properties:

SessionMode

A mode the agent can operate in. See protocol docs: Session Modes Type: Object Properties:

SessionModeId

Unique identifier for a Session Mode. Type: string

SessionModeState

The set of modes and the one currently active. Type: Object Properties:

SessionResumeCapabilities

Capabilities for the session/resume method. Supplying \{\} means the agent supports resuming sessions. Type: Object Properties:

SessionSystemPromptCapabilities

Capabilities for client-provided system prompts. Supplying \{\} means the agent supports systemPrompt on session lifecycle requests in append mode. Type: Object Properties:

SessionSystemPromptModeCapabilities

System prompt delivery modes the agent supports in addition to append. append has no entry because every agent advertising sessionCapabilities.systemPrompt supports it. Type: Object Properties:

SessionSystemPromptOverrideCapabilities

Capabilities for the override system prompt mode. Supplying \{\} means the agent supports replacing its built-in default instructions with the client-provided system prompt. Type: Object Properties:

SessionUpdate

Different types of updates that can be sent during session processing. These updates provide real-time feedback about the agent’s progress. See protocol docs: Agent Reports Output Type: Union

StopReason

Reasons why an agent stops processing a prompt turn. See protocol docs: Stop Reasons Type: Union

StringFormat

String format types for string properties in elicitation schemas. Type: Union

StringMultiSelectItems

String item schema for multi-select enum properties. Type: Object Properties:

StringPropertySchema

Schema for string properties in an elicitation form. When enum or oneOf is set, this represents a single-select enum with "type": "string". Type: Object Properties:

SystemPrompt

Client-provided system-level instructions for a session. Clients MUST only send this when the Agent advertises sessionCapabilities.systemPrompt. Agents that cannot apply it, for example because of an unadvertised mode or an unsupported content block type, MUST return an error instead of creating, loading, or resuming the session. Type: Object Properties:

SystemPromptMode

How the Agent combines a client-provided system prompt with its own instructions. Unknown modes are preserved so they can be stored, proxied, or forwarded. An Agent MUST return an error for a mode it does not support rather than treating it as append or override. Type: Union

Terminal

Embed a terminal created with terminal/create by its id. The terminal must be added before calling terminal/release. See protocol docs: Terminal Type: Object Properties:

TerminalExitStatus

Exit status of a terminal command. Type: Object Properties:

TerminalId

Typed identifier used for terminal values on the wire. Type: string

TextContent

Text provided to or from an LLM. Type: Object Properties:

TextResourceContents

Text-based resource contents. Type: Object Properties:

TitledMultiSelectItems

Items definition for titled multi-select enum properties. Type: Object Properties:

ToolCall

Represents a tool call that the language model has requested. Tool calls are actions that the agent executes on behalf of the language model, such as reading files, executing code, or fetching data from external sources. See protocol docs: Tool Calls Type: Object Properties:

ToolCallContent

Content produced by a tool call. Tool calls can produce different types of content including standard content blocks (text, images) or file diffs. See protocol docs: Content Type: Union

ToolCallId

Unique identifier for a tool call within a session. Type: string

ToolCallLocation

A file location being accessed or modified by a tool. Enables clients to implement “follow-along” features that track which files the agent is working with in real-time. See protocol docs: Following the Agent Type: Object Properties:

ToolCallStatus

Execution status of a tool call. Tool calls progress through different statuses during their lifecycle. See protocol docs: Status Type: Union

ToolCallUpdate

An update to an existing tool call. Used to report progress and results as tools execute. All fields except the tool call ID are optional - only changed fields need to be included. See protocol docs: Updating Type: Object Properties:

ToolKind

Categories of tools that can be invoked. Tool kinds help clients choose appropriate icons and optimize how they display tool execution progress. See protocol docs: Creating Type: Union

UnstructuredCommandInput

All text that was typed after the command name is provided as input. Type: Object Properties:

UsageUpdate

Context window and cost update for a session. Type: Object Properties: