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MCP: Validate tool name uniqueness across BuiltIn and Custom tools#3110

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souvikghosh04 merged 7 commits intomainfrom
copilot/handle-duplicate-tool-names
Feb 11, 2026
Merged

MCP: Validate tool name uniqueness across BuiltIn and Custom tools#3110
souvikghosh04 merged 7 commits intomainfrom
copilot/handle-duplicate-tool-names

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Copilot AI commented Feb 6, 2026 •
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Why make this change?

MCP tool names must be unique. Without validation, custom tools (generated from stored procedure entities) could conflict with built-in tools (create_record, read_records, etc.) or other custom tools, causing undefined behavior during tool invocation.

What is this change?

Added duplicate detection in McpToolRegistry.RegisterTool() that throws DataApiBuilderException on conflict:

// Check for duplicate tool names
if (_tools.TryGetValue(metadata.Name, out IMcpTool? existingTool))
{
    string existingToolType = existingTool.ToolType == ToolType.BuiltIn ? "built-in" : "custom";
    string newToolType = tool.ToolType == ToolType.BuiltIn ? "built-in" : "custom";
    
    throw new DataApiBuilderException(
        message: $"Duplicate MCP tool name '{metadata.Name}' detected. " +
                 $"A {existingToolType} tool with this name is already registered. " +
                 $"Cannot register {newToolType} tool with the same name. " +
                 $"Tool names must be unique across all tool types.",
        statusCode: HttpStatusCode.ServiceUnavailable,
        subStatusCode: DataApiBuilderException.SubStatusCodes.ErrorInInitialization);
}

Files Modified:

  • McpToolRegistry.cs: Added validation in RegisterTool()

Files Added:

  • McpToolRegistryTests.cs: 12 test cases covering duplicate detection across tool types, case sensitivity, and error messaging

Validation occurs during McpToolRegistryInitializer.StartAsync() ensuring fail-fast at service startup.

How was this tested?

  • Unit Tests

Sample Request(s)

N/A - Internal validation, no user-facing API changes

Original prompt

This section details on the original issue you should resolve

<issue_title>MCP-CustomTool: Handle duplicate tool names, if any</issue_title>
<issue_description>MCP tool names should be unique. Custom tools when configured and exposed should not be duplicate and conflict with existing tool names.

  • MCP tools should not be duplicate
  • Tools of both types- BuiltInTool and DynamicCustomTool should be unique
  • This should be detected and validated during tools registration
  • Appropriate error message should be provided to user if that happens so that user can fix it
  • Add supporting tests with good code coverage and different scenarios and edge cases</issue_description>

<agent_instructions>- Refer to the description and comments

  • Implement the changes and make sure existing functionality is not broken
  • Create a Pull Request</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@JerryNixon Remember tool names are based on Entity aliases which are already required to be unique.

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

Copilot AI changed the title [WIP] Handle duplicate tool names for MCP tools MCP: Validate tool name uniqueness across BuiltIn and Custom tools Feb 6, 2026
Copilot AI requested a review from souvikghosh04 February 6, 2026 06:44
@souvikghosh04 souvikghosh04 added this to the Feb 2026 milestone Feb 6, 2026
@souvikghosh04 souvikghosh04 added mssql an issue thats specific to mssql mcp-server labels Feb 6, 2026
@souvikghosh04 souvikghosh04 marked this pull request as ready for review February 6, 2026 07:03
Copilot AI review requested due to automatic review settings February 6, 2026 07:03
Copilot AI reviewed Feb 6, 2026
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Pull request overview

This PR adds validation to ensure MCP tool names are unique across both built-in and custom tool types. Without this validation, custom tools (generated from stored procedure entities) could conflict with built-in tools like create_record or read_records, causing undefined behavior during tool invocation.

Changes:

  • Added duplicate tool name detection in McpToolRegistry.RegisterTool() that throws DataApiBuilderException when a conflict is detected
  • Implemented comprehensive test suite with 12 test cases covering various duplicate scenarios, case sensitivity, and error messaging

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File Description
src/Azure.DataApiBuilder.Mcp/Core/McpToolRegistry.cs Added validation logic to detect and reject duplicate tool names across BuiltIn and Custom tool types
src/Service.Tests/Mcp/McpToolRegistryTests.cs New test file with comprehensive coverage of duplicate detection scenarios, case sensitivity, and edge cases

@souvikghosh04 souvikghosh04 moved this from Todo to Review In Progress in Data API builder Feb 6, 2026
anushakolan
anushakolan requested changes Feb 6, 2026
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Comment thread src/Service.Tests/Mcp/McpToolRegistryTests.cs Outdated
Comment thread src/Azure.DataApiBuilder.Mcp/Core/McpToolRegistry.cs
Comment thread src/Azure.DataApiBuilder.Mcp/Core/McpToolRegistry.cs
Comment thread src/Service.Tests/Mcp/McpToolRegistryTests.cs
Comment thread src/Service.Tests/Mcp/McpToolRegistryTests.cs Outdated
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anushakolan commented Feb 6, 2026

/azp run

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azure-pipelines Bot commented Feb 6, 2026

Azure Pipelines successfully started running 6 pipeline(s).

@anushakolan anushakolan self-assigned this Feb 6, 2026
Aniruddh25
Aniruddh25 reviewed Feb 6, 2026
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Comment thread src/Service.Tests/Mcp/McpToolRegistryTests.cs Outdated
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Comment thread src/Service.Tests/Mcp/McpToolRegistryTests.cs Outdated
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Comment thread src/Service.Tests/Mcp/McpToolRegistryTests.cs
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Reducing the test matrix to what is really possible.

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Aniruddh25 commented Feb 11, 2026

/azp run

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azure-pipelines Bot commented Feb 11, 2026

Azure Pipelines successfully started running 6 pipeline(s).

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souvikghosh04 commented Feb 11, 2026

/azp run

@souvikghosh04 souvikghosh04 enabled auto-merge (squash) February 11, 2026 14:26
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Azure Pipelines successfully started running 6 pipeline(s).

anushakolan
anushakolan approved these changes Feb 11, 2026
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LGTM!

@souvikghosh04 souvikghosh04 merged commit 20df64c into main Feb 11, 2026
11 checks passed
@souvikghosh04 souvikghosh04 deleted the copilot/handle-duplicate-tool-names branch February 11, 2026 21:38
@github-project-automation github-project-automation Bot moved this from Review In Progress to Done in Data API builder Feb 11, 2026
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Reviewers

Copilot code review Copilot Copilot left review comments

@Aniruddh25 Aniruddh25 Aniruddh25 approved these changes

@anushakolan anushakolan anushakolan approved these changes

@souvikghosh04 souvikghosh04 Awaiting requested review from souvikghosh04 souvikghosh04 is a code owner

@aaronburtle aaronburtle Awaiting requested review from aaronburtle aaronburtle is a code owner

@RubenCerna2079 RubenCerna2079 Awaiting requested review from RubenCerna2079 RubenCerna2079 is a code owner

@neeraj-sharma2592 neeraj-sharma2592 Awaiting requested review from neeraj-sharma2592

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Labels

2.0 mcp-server mssql an issue thats specific to mssql

Projects

Data API builder
Status: Done

Milestone

Feb 2026

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Successfully merging this pull request may close these issues.

MCP-CustomTool: Handle duplicate tool names, if any

5 participants

@anushakolan @Aniruddh25 @souvikghosh04