fix(api): use camelCase in CallToolResponse and add type discriminators to ContentBlock by aharvard · Pull Request #7487 · block/goose

aharvard · 2026-02-24T19:08:32Z

Summary

Fixes the CallToolResponse API to use camelCase field names matching the MCP spec, and adds proper type discriminator fields to content blocks so generated TypeScript types align with the SDK's CallToolResult.

Problem

CallToolResponse serialized fields as snake_case (is_error, structured_content) but the MCP spec and SDK expect camelCase (isError, structuredContent)
The Content type from rmcp includes a type discriminator on the wire (via #[serde(tag = "type")]) but utoipa can't reflect this for external types, so the generated OpenAPI schema and TypeScript types were missing it
McpAppToolResult was a redundant intermediate type that duplicated CallToolResult

Changes

Rust Backend (agent.rs):

Added #[serde(rename_all = "camelCase")] to CallToolResponse
Changed content to Vec<Value> with schema-only ContentBlock types that include type discriminator literals ("text", "image", "resource", "audio", "resource_link")
Manual ToSchema impls to work around utoipa's inability to reflect rmcp's #[serde(tag = "type")]

Frontend:

Removed redundant McpAppToolResult type
McpAppRenderer now accepts CallToolResult directly — no conversion useMemo
ToolCallWithResponse uses ContentBlock (with proper type field) instead of old Content

Why schema-only types?

rmcp's schemars schema is correct (it reflects the type discriminator), but goose uses utoipa for OpenAPI generation. utoipa can't derive the right schema for rmcp's externally-defined tagged enum. The schema-only types exist solely to produce a correct OpenAPI spec — actual serialization goes through serde_json::Value.

Follows up on #7476

Copilot

Pull request overview

Updates the server and desktop UI API types to match the MCP wire spec by emitting camelCase fields for CallToolResponse and ensuring tool content blocks are OpenAPI-discriminated unions (with a literal type field), so generated TypeScript aligns with the SDK’s CallToolResult.

Changes:

Backend: serialize CallToolResponse in camelCase and introduce schema-only ContentBlock variants with type discriminators for OpenAPI/TS generation.
Frontend: remove the redundant McpAppToolResult and pass CallToolResult through to AppRenderer directly.
Regenerate OpenAPI + TypeScript client types to reflect the corrected response shape.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
ui/desktop/src/components/ToolCallWithResponse.tsx	Switches tool result handling to `ContentBlock` and adjusts embedded resource rendering.
ui/desktop/src/components/McpApps/types.ts	Removes the redundant `McpAppToolResult` type.
ui/desktop/src/components/McpApps/McpAppRenderer.tsx	Accepts `CallToolResult` directly and updates `callTool` response field names to camelCase.
ui/desktop/src/api/types.gen.ts	Regenerated types: `CallToolResponse` camelCase + new `ContentBlock` discriminated union.
ui/desktop/src/api/index.ts	Re-exports newly generated API types (including `ContentBlock` variants).
ui/desktop/openapi.json	OpenAPI schema updated for camelCase fields and discriminated `ContentBlock` schemas.
crates/goose-server/src/routes/agent.rs	Implements camelCase `CallToolResponse` + schema-only content block schemas and serializes content via `Value`.
crates/goose-server/src/openapi.rs	Registers the new schema-only content block schemas for OpenAPI generation.

ui/desktop/src/components/ToolCallWithResponse.tsx

crates/goose-server/src/routes/agent.rs

ui/desktop/src/components/McpApps/McpAppRenderer.tsx

Copilot

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.

DOsinga · 2026-02-25T15:44:51Z

Why schema-only types?

I am not sure about this. It looks complicated and since it constructs the types independently of the actual Rust code, only give us the illusion of type safety

aharvard · 2026-02-25T15:56:45Z

Why schema-only types?

I am not sure about this. It looks complicated and since it constructs the types independently of the actual Rust code, only give us the illusion of type safety

The goal is to get a discriminated union for TS, the current way RMCP approaches this lacks the type field to discriminate from. Do you think there something we can adjust in RMCP that makes both Rust and our generated types happier? cc @alexhancock

jamadeo · 2026-03-10T19:18:50Z

@aharvard I pulled your branch and tried adding support to the existing schemars-to-utoipa macros we have in openapi.rs, and I think the result looks like what we want: #7792 (that's a PR targeting this branch)

Feel free to merge it into this if it accomplishes what you're doing. The types are defined slightly differently, but you still get a discriminated union at the end

aharvard · 2026-03-10T20:35:01Z

thanks @jamadeo, just merged in your PR (will work on cleaning up this PR next)

…rs to ContentBlock - Add #[serde(rename_all = "camelCase")] to CallToolResponse so fields serialize as isError, structuredContent (matching MCP spec) - Define schema-only ContentBlock types with proper 'type' discriminator fields (text, image, resource, audio, resource_link) for OpenAPI - Serialize content via serde_json::Value to bypass utoipa's inability to reflect rmcp's #[serde(tag = "type")] on external types - Replace old Content type with ContentBlock in ToolCallWithResponse - Remove redundant McpAppToolResult type; use CallToolResult directly in McpAppRenderer Co-authored-by: Goose <[email protected]> Ai-assisted: true

Co-authored-by: Goose <[email protected]> Ai-assisted: true

@DOsinga

* main: (45 commits) fix: resolve {{ recipe_dir }} in nested sub-recipe paths during secret discovery (#7797) Add @DOsinga as CODEOWNER for documentation (#7799) feat: Add summarize tool for deterministic reads (#7054) fix(api): use camelCase in CallToolResponse and add type discriminators to ContentBlock (#7487) feat: ACP providers for claude code and codex (#6605) chore(deps): bump express-rate-limit from 8.2.1 to 8.3.0 in /evals/open-model-gym/mcp-harness (#7703) feat(openai): capture reasoning summaries from responses API (#7375) Fix some dependencies (#7794) fix: improve keyring availability error detection (#7766) feat: add MiniMax provider with Anthropic-compatible API (#7640) feat: add Tensorix as a declarative provider (#7712) fix(security): remove insecure default secret from GOOSE_EXTERNAL_BACKEND (#7783) refactor: Convert Tanzu provider to declarative JSON config (#7124) replaces https://github.com/block/goose/pull/7340/changes (#7786) feat(summon): make skill supporting files individually loadable via load() (#7583) Keep toast open on failed extension (#7771) fix(ui-desktop): unify path resolution around GOOSE_PATH_ROOT (#7335) fix: pass OAuth scopes to DCR and extract granted_scopes from token response (#7571) fix: write to real file if config.yaml is symlink (#7669) fix: preserve pairings when stopping gateway (#7733) ...

@DOsinga

* main: (69 commits) fix: resolve {{ recipe_dir }} in nested sub-recipe paths during secret discovery (#7797) Add @DOsinga as CODEOWNER for documentation (#7799) feat: Add summarize tool for deterministic reads (#7054) fix(api): use camelCase in CallToolResponse and add type discriminators to ContentBlock (#7487) feat: ACP providers for claude code and codex (#6605) chore(deps): bump express-rate-limit from 8.2.1 to 8.3.0 in /evals/open-model-gym/mcp-harness (#7703) feat(openai): capture reasoning summaries from responses API (#7375) Fix some dependencies (#7794) fix: improve keyring availability error detection (#7766) feat: add MiniMax provider with Anthropic-compatible API (#7640) feat: add Tensorix as a declarative provider (#7712) fix(security): remove insecure default secret from GOOSE_EXTERNAL_BACKEND (#7783) refactor: Convert Tanzu provider to declarative JSON config (#7124) replaces https://github.com/block/goose/pull/7340/changes (#7786) feat(summon): make skill supporting files individually loadable via load() (#7583) Keep toast open on failed extension (#7771) fix(ui-desktop): unify path resolution around GOOSE_PATH_ROOT (#7335) fix: pass OAuth scopes to DCR and extract granted_scopes from token response (#7571) fix: write to real file if config.yaml is symlink (#7669) fix: preserve pairings when stopping gateway (#7733) ...

Copilot AI review requested due to automatic review settings February 24, 2026 19:08

Copilot started reviewing on behalf of aharvard February 24, 2026 19:09 View session

aharvard force-pushed the fix/call-tool-response-camelcase branch from 4baca4a to 74e2d8e Compare February 24, 2026 19:13

Copilot AI reviewed Feb 24, 2026

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ui/desktop/src/components/ToolCallWithResponse.tsx Outdated Show resolved Hide resolved

crates/goose-server/src/routes/agent.rs Outdated Show resolved Hide resolved

ui/desktop/src/components/McpApps/McpAppRenderer.tsx Show resolved Hide resolved

aharvard marked this pull request as draft February 24, 2026 19:15

aharvard force-pushed the fix/call-tool-response-camelcase branch from 74e2d8e to 00dfded Compare February 24, 2026 19:41

aharvard marked this pull request as ready for review February 24, 2026 21:48

Copilot AI review requested due to automatic review settings February 24, 2026 21:48

Copilot started reviewing on behalf of aharvard February 24, 2026 21:49 View session

aharvard mentioned this pull request Feb 24, 2026

fix(apps): forward _meta in tool results to MCP Apps #7476

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Copilot AI reviewed Feb 24, 2026

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aharvard requested review from DOsinga, alexhancock, jamadeo, katzdave, michaelneale and zanesq February 25, 2026 13:56

DOsinga assigned jamadeo Mar 9, 2026

aharvard and others added 3 commits March 10, 2026 16:37

Add discriminated union handling to schema generation (#7792)

8bf2c52

Co-authored-by: Goose <[email protected]> Ai-assisted: true

fix(ui): restore OnDisplayModeChange type after conflict resolution

fe0dfd3

Co-authored-by: Goose <[email protected]> Ai-assisted: true

aharvard force-pushed the fix/call-tool-response-camelcase branch from b96683e to fe0dfd3 Compare March 10, 2026 20:46

aharvard and others added 3 commits March 10, 2026 16:52

chore: regenerate openapi types after rebase

cf77d7a

Co-authored-by: Goose <[email protected]> Ai-assisted: true

chore(ui): remove stale comment about ContentBlock type mismatch

a8567fb

Co-authored-by: Goose <[email protected]> Ai-assisted: true

chore: remove stale comment in ToolCallWithResponse

6daed64

Co-authored-by: Goose <[email protected]> Ai-assisted: true

jamadeo approved these changes Mar 11, 2026

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aharvard added this pull request to the merge queue Mar 11, 2026

Merged via the queue into main with commit 76e4966 Mar 11, 2026
19 of 21 checks passed

aharvard deleted the fix/call-tool-response-camelcase branch March 11, 2026 00:45

github-actions bot mentioned this pull request Mar 16, 2026

chore(release): release version 1.28.0 (minor) #7780

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fix(api): use camelCase in CallToolResponse and add type discriminators to ContentBlock#7487

fix(api): use camelCase in CallToolResponse and add type discriminators to ContentBlock#7487
aharvard merged 6 commits intomainfrom
fix/call-tool-response-camelcase

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aharvard commented Feb 24, 2026

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Why schema-only types?

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DOsinga commented Feb 25, 2026

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