fix(mcp): pass tool outputSchema to Vercel AI SDK dynamicTool

[wucm667]

Fixes #1956

Problem

When an MCP server declares a tool with an outputSchema, the inspector reads it for client-side validation and UI display, but does NOT include it in the structured tool definitions sent to the LLM via the Vercel AI SDK. As a result, the LLM cannot interpret custom response fields defined in the output schema.

Changes

• File 1: sdk/src/mcp-client-manager/tool-converters.ts

  • Extract outputSchema from the MCP tool description alongside name, description, and inputSchema
  • Pass outputSchema to dynamicTool() when available (automatic mode)

• File 2: sdk/src/TestAgent.ts

  • Same fix: include outputSchema in the dynamicTool() call for the test agent's tool conversion

Impact

Before this fix, an MCP tool like:

@mcp.tool()
def get_weather(city: str) -> WeatherData:
    ...

Where WeatherData has a custom field x: int, would not pass the output schema to the LLM. The LLM could not interpret the x field in the response.

After this fix, the output schema is included in the tool definition, allowing the LLM to correctly understand and use all response fields.

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[chelojimenez]

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ℹ️ Recent review info

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Configuration used: Organization UI

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📥 Commits

Reviewing files that changed from the base of the PR and between 621323b and a1f80ed.

📒 Files selected for processing (2)

• sdk/src/TestAgent.ts
• sdk/src/mcp-client-manager/tool-converters.ts

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Walkthrough

This change enhances tool conversion by introducing support for outputSchema. The conversion mechanism now extracts outputSchema from MCP tool descriptions and forwards it to Vercel's dynamicTool configuration in automatic conversion scenarios. When an outputSchema is present, it gets passed through; otherwise, the existing behavior is preserved. The change affects tool configuration within the SDK's tool conversion pipeline, enabling more complete schema information to be carried through the conversion process.

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[chelojimenez]

thanks for putting this up @wucm667! i'll merge this tomorrow 🫡