arktype•7d ago

Zod Interop?

I'm seeing a lot of MCP tools exposing Zod-based APIs, which is annoying. I'm sure this has been discussed before, but is there a way to use an Arktype schema in place of Zod? Here's an example from https://github.com/punkpeye/fastmcp where Zod is used but I'd like to use Arktype:

server.addTool({
  name: "add",
  description: "Add two numbers",
  parameters: z.object({
    a: z.number(),
    b: z.number(),
  }),
  execute: async (args) => {
    return String(args.a + args.b);
  },
});

server.addTool({
  name: "add",
  description: "Add two numbers",
  parameters: z.object({
    a: z.number(),
    b: z.number(),
  }),
  execute: async (args) => {
    return String(args.a + args.b);
  },
});

The screenshot is another example from https://modelcontextprotocol.io/quickstart/server

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GitHub - punkpeye/fastmcp: A TypeScript framework for building MCP ...

A TypeScript framework for building MCP servers. Contribute to punkpeye/fastmcp development by creating an account on GitHub.

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5 Replies

jacksteamdevOP•7d ago

I made an issue here for FastMCP to adopt Standard Schema https://github.com/punkpeye/fastmcp/issues/26 and there's this MCP issue with a WIP PR https://github.com/modelcontextprotocol/typescript-sdk/issues/164, but I'm wondering if there's a workaround in place.

GitHub

Replace Zod with Standard Schema for validation · Issue #26 · pun...

Background FastMCP currently uses Zod directly for schema validation. However, the Standard Schema specification has been developed as a common interface for JavaScript/TypeScript schema libraries....

GitHub

Issues · modelcontextprotocol/typescript-sdk

The official Typescript SDK for Model Context Protocol servers and clients - Issues · modelcontextprotocol/typescript-sdk

ssalbdivad•4d ago

Definitely think getting these APIs to use StandardSchema is key, but it would be pretty to publish a package that just wrapped ArkType in a .superRefine or something and cast it to a corresponding ZodType? Depends a bit on whether those MCP APIs are introspecting the schema at all or just using it for validation.

jacksteamdevOP•3d ago

FastMCP now supports StandardSchema validators https://github.com/punkpeye/fastmcp/pull/27

GitHub

Switch from Zod to Standard Schema by jacksteamdev · Pull Request ...

Overview This PR replaces direct Zod usage with Standard Schema support, allowing users to choose their preferred validation library while maintaining existing functionality. Changes Added @standa...

ssalbdivad•3d ago

Sweet! Thanks for tackling this 😊 Feels like the TS ecosystem has been super quick to adopt standard schema but AI is definitely lagging a few years behind

Dimava•19h ago

AI needs toJsonSchema because it needs that for schema-aware generation Do yall plan to add it to standard schema?

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Zod Interop?

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