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Drop the zod 3 JSON Schema fallback

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The zod peer range is ^4.2.0, whose schemas implement
~standard.jsonSchema, so the lazy zod/v4 toJSONSchema fallback for
zod 3.25 is dead code. Re-export StandardSchemaWithJSON from the client
package instead of keeping a structurally identical local copy.
This commit is contained in:
Olivier Chafik 2026-09-07 15:29:42 +01:00
commit 09bf2aae3c
1 changed files with 11 additions and 33 deletions
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44
src/standard-schema.ts
View file

@ -4,36 +4,22 @@ import type {
StandardTypedV1,
} from "@standard-schema/spec";
export type { StandardJSONSchemaV1, StandardSchemaV1, StandardTypedV1 };
// TODO(sdk-v2): once @modelcontextprotocol/core v2 is stable, import
// StandardSchemaWithJSON / standardSchemaToJsonSchema / validateStandardSchema
// from there and delete this file. At that point decide whether to tighten
// App.registerTool to StandardSchemaWithJSON (drops zod 3 from the peer range
// and the lazy z.toJSONSchema fallback below).
import type { StandardSchemaWithJSON } from "@modelcontextprotocol/client";
/**
* A schema that implements both Standard Schema (validation) and Standard JSON
* Schema (serialization). Zod v4, ArkType, and Valibot (via
* `@valibot/to-json-schema`) all satisfy this.
*
* Mirrors the type of the same name in `@modelcontextprotocol/core` v2 so that
* bumping to that package later is a drop-in import swap.
* `@valibot/to-json-schema`) all satisfy this. Re-exported from the SDK so
* View authors can import it alongside {@link app!App `App`}.
*
* @see https://standardschema.dev/
* @see https://github.com/modelcontextprotocol/typescript-sdk/pull/1689
*/
export interface StandardSchemaWithJSON<Input = unknown, Output = Input> {
readonly "~standard": StandardSchemaV1.Props<Input, Output> &
StandardJSONSchemaV1.Props<Input, Output>;
}
export namespace StandardSchemaWithJSON {
export type InferInput<S extends StandardTypedV1> =
StandardTypedV1.InferInput<S>;
export type InferOutput<S extends StandardTypedV1> =
StandardTypedV1.InferOutput<S>;
}
export type {
StandardJSONSchemaV1,
StandardSchemaV1,
StandardSchemaWithJSON,
StandardTypedV1,
};
/** JSON-Schema target draft used for tool input/output schemas (matches core MCP). */
const TARGET = { target: "draft-2020-12" } as const;
@ -41,11 +27,8 @@ const TARGET = { target: "draft-2020-12" } as const;
/**
* Serialize a Standard Schema to JSON Schema for the given direction.
*
* Uses `~standard.jsonSchema` when present (zod v4, ArkType, Valibot, …).
* Falls back to a lazy `zod/v4` import for zod v3.25.x — which implements
* `~standard.validate` but not yet `~standard.jsonSchema` — so the existing
* `^3.25.0 || ^4.0.0` peer range keeps working. Non-zod schemas without
* `jsonSchema` throw.
* Requires `~standard.jsonSchema` (zod v4, ArkType, Valibot, …); schemas
* without it throw.
*/
export async function standardSchemaToJsonSchema(
schema: StandardSchemaV1,
@ -57,11 +40,6 @@ export async function standardSchemaToJsonSchema(
if (std.jsonSchema) {
return std.jsonSchema[io](TARGET);
}
if (std.vendor === "zod") {
const { z } = await import("zod/v4");
// eslint-disable-next-line @typescript-eslint/no-explicit-any -- bridging StandardSchemaV1 → zod's $ZodType for the v3.25 fallback
return z.toJSONSchema(schema as any, { io });
}
throw new Error(
`Schema (vendor: ${std.vendor}) does not implement Standard JSON Schema (~standard.jsonSchema). ` +
`Use a library that does (zod v4, ArkType, Valibot) or wrap your schema accordingly.`,