Adopting Standard Schema

[harrysolovay]

Is your feature request related to a problem? Please describe.

This SDK seems quite coupled to zod. The creator of zod as well as the creators of other popular virtual TS type libs partnered to define the Standard Schema Spec. Given that a lot of these virtual type libs enable JSON schema generation, I see no reason for this SDK to be coupled to zod directly.

Describe the solution you'd like

Let's consider the tool method signature:

tool<Args extends ZodRawShape>(name: string, description: string, paramsSchema: Args, cb: ToolCallback<Args>): void;

This could instead be declared as the following:

tool<Args extends object>(name: string, description: string, paramsSchema: StandardSchemaV1 <Args>, cb: ToolCallback<Args>): void;

^ This isn't exactly what it would need to be, as different virtual type libraries are converted to JSON in different ways... but it's the gist. The real implementation would likely involve a wrapper function and type, similar to Hono's standard validator. Ie. users would wrap their virtual type with an adapter that simply calls whatever JSON-producing method of the virtual type (in this case, an arktype.

import { type } from "arktype"
import { schema } from "arktype-mcp"
//                     ^ hypothetical lib

const MyType = type({
  a: "string | number",
  "b?": {
    c: "'d'"
  },
  e: ["'f'", "'g'"]
})

tool(NAME, DESC, schema(MyType), (v) => {
  v satisfies {
    a: string | number;
    b: {
        c: "d";
    };
    e: ["f", "g"];
  }
})

Describe alternatives you've considered

Virtual type libraries are a critical utility for ensuring a single source of truth. But Zod is not necessarily the best choice depending on use case / preferences. I personally prefer arktype, which is more versatile for modeling nested types, custom scopes and type-safe cycles.

Additional context

• https://arktype.io
• https://valibot.dev
• https://effect.website/docs/schema/introduction/
• https://github.com/modiimedia/arri
• https://github.com/sinclairzx81/typemap
• https://github.com/GauBen/formgator
• https://github.com/nvie/decoders
• https://github.com/DZakh/rescript-schema
• https://github.com/skunkteam/types

^ All of these implement standard schema and can have their static types extracted via T["~standard"], where T is any virtual type.

[nbbaier]

Really want to see this.

[harrysolovay]

I'd like to go through this codebase and do a few things:

1. Update user-facing signatures such that T extends StandardSchemaV1 instead of T extends ZodRawShape.
2. Update any zod parses calls with StandardSchemaV1["~standard"].validate.
3. Update any JSON-schema-producing code to use a general-purpose runtime-type-agnostic toJSONSchema util (created with this use case in mind).

This will enable developers to use their runtime type libraries of choice / help with consistency in projects that do not use zod.

If there's sufficient interest in this solution, let me know and I'll submit a PR :)

@jspahrsummers would this be acceptable?

[qcho]

I'd love to see this implemented; adopting standard-schema designed by the creators of Zod, Valibot, and ArkType will enable this sdk to interoperate with any codebase.

I understand that there is another important issue ejecting from zod that is zod-to-json-schema.
In my case using Valibot I would use @valibot/to-json-schema but standard-schema

There is no good solution right now from standard-schema to support toJSONSchema or anything similar.

Edit: just realized you authored standard-json-schema ^_^. Looks promising with the peer-dependency approach i would install sdk(including std schema and your lib)+valibot@peer + @valibot/to-json-schema@peer

[jspahrsummers]

Sure, this seems useful. Happy to review a PR here.

[harrysolovay]

Awesome! Just opened a draft PR. Still some quirks to iron out. Looking forward to hearing your thoughts.

[robahtou]

Not sure if this is the right place. I'm new to the MCP and started to work with the TS sdk. And like OP I was kinda irked by the tightly coupling of Zod. Would the solution being advertise allow me to use AJV? We have so many projects with this library and code gen tools utilizing JSON Schemas.