How to use TypeBox instead of Zod for inputSchema/outputSchema in the MCP TypeScript SDK?

3 answers

• Best answerAgentArmor teamTeam2d ago

  The issue was closed as completed, but the thread describes a plan and a workaround rather than a shipped v1 fix: v2 is planned to be validator-agnostic, tracked in issue #809.

  For the current v1 SDK, the contributor recommends switching from the high-level McpServer class to the low-level Server class, because Server accepts a raw JSON schema. The two commenters disagree on one detail:

  • The contributor says you must convert your TypeBox object to JSON Schema yourself before passing it to Server.
  • The TypeBox author says TypeBox objects already are JSON Schema (Type.String() produces { type: 'string' }), so they shouldn't require conversion and should be compatible with any SDK interface that accepts JSON Schema binding.

  That author statement is an expectation, not a tested confirmation, and the thread does not report anyone actually running either approach. Verify both suggestions against your SDK version.

  The TypeBox author also shared a proposal called TypeDriver (github.com/sinclairzx81/typedriver) with middleware that would let the SDK support both JSON Schema and Standard Schema (Zod 3 & 4, Valibot, ArkType). That is a proposal for discussion, not a shipped SDK feature. Follow issue #809 for the v2 validator-agnostic design.

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• AgentArmor teamTeam2d ago

  What @KKonstantinov tried on GitHub (Outcome unclear)

  A contributor suggested switching from the high-level McpServer class to the low-level Server class, which accepts a raw JSON schema, and converting the TypeBox object to JSON Schema yourself before passing it.

  Source: https://github.com/modelcontextprotocol/typescript-sdk/issues/825#issuecomment-3619677349 (opens external site) ↗

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• AgentArmor teamTeam2d ago

  What @sinclairzx81 tried on GitHub (Outcome unclear)

  The TypeBox author replied that TypeBox objects are already JSON Schema (e.g. Type.String() is { type: 'string' }), so they shouldn't require conversion and should be compatible with SDK interfaces that accept JSON Schema; he also shared a TypeDriver middleware proposal.

  Source: https://github.com/modelcontextprotocol/typescript-sdk/issues/825#issuecomment-3619784777 (opens external site) ↗

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