Switch from Zod to Standard Schema

[jacksteamdev]

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 @standard-schema/spec and xsschema dependencies
• Updated ToolParameters type to use StandardSchemaV1
• Replaced zodToJsonSchema with toJsonSchema

Benefits

• Users can now use any schema library that implements Standard Schema (Zod, Valibot, ArkType)
• Aligns with ecosystem direction supported by schema library creators
• Follows the example of libraries like tRPC, TanStack Form, and others adopting Standard Schema

Todo

• Implement Standard Schema support
• Update README with examples
• Add usage examples for different schema libraries

Related Issues

Resolves #26

[jacksteamdev]

This library is a peer dependency of xsschema and isn't strictly required anymore but I left it because removing it would be a breaking change for Zod users.

[qcho]

I would remove it. The whole idea behind all of this is not to add a new dependency all-together.
And it won't break in runtime but at the install moment. Seems safe enough.

[punkpeye]

@jacksteamdev Awesome contribution. Thank you ❤️

[jacksteamdev]

@punkpeye Happy to help. Thanks for all your work in the MCP scene!

[qcho]

I would remove it. The whole idea behind all of this is not to add a new dependency all-together.
And it won't break in runtime but at the install moment. Seems safe enough.

[qcho]

adding all of these dependencies seems wrong.
They should be optional peer dependencies.

[jacksteamdev]

These are dev dependencies for src/examples/addition.ts

[ryoppippi]

I agree @qcho we need to add @valibot/to-json-schema to optional peer deps.
And, I'd love to add zod/zod-to-json-schema to peer deps

[LunreMore]

Core Issue: When a single bundle file is too large, asynchronously importing dependencies can significantly increase loading time. If the server is started before asynchronous loading is complete, toJsonSchema will be undefined.

FastMCP registers multiple tools upon startup. Each tool's parameter definition (such as Zod, ArkType, and Valibot schema) triggers the asynchronous import mechanism of xsschema. xsschema dynamically loads a converter library (such as zod-to-json-schema and @valibot/to-json-schema) based on the schema type. The schema is then converted to JSON Schema for tool parameter validation. Finally, the server is started and the client waits for calls.

It is recommended to precompile the package for static import, or at least check and wait for the package to be imported before calling toJsonSchema.