feat: Support Standard Schema

README.md

@@ -47,10 +47,12 @@ The Model Context Protocol allows applications to provide context for LLMs in a
 ## Installation
 
 ```bash
-npm install @modelcontextprotocol/sdk zod
+npm install @modelcontextprotocol/sdk
+# plus your preferred Standard Schema library, e.g.
+npm install zod            # if you follow the Zod examples below
 ```
 
-This SDK has a **required peer dependency** on `zod` for schema validation. The SDK internally imports from `zod/v4`, but maintains backwards compatibility with projects using Zod v3.25 or later. You can use either API in your code by importing from `zod/v3` or `zod/v4`:
+The SDK speaks [Standard Schema](https://standardschema.dev/) for validation. Bring any Standard Schema-compatible library (Zod, Valibot, ArkType, etc). Examples below use Zod, and the SDK still supports both Zod v3.25+ and v4.
 
 ## Quick Start
 
@@ -161,6 +163,8 @@ const server = new McpServer({
 [Tools](https://modelcontextprotocol.io/specification/latest/server/tools) let LLMs take actions through your server. Tools can perform computation, fetch data and have side effects. Tools should be designed to be model-controlled - i.e. AI models will decide which tools to call,
 and the arguments.
 
+Tool schemas accept any Standard Schema validator. The SDK converts Standard Schemas to JSON Schema for clients (Zod, Valibot, ArkType, etc).
+
 ```typescript
 // Simple tool with parameters
 server.registerTool(

package.json

@@ -78,6 +78,9 @@
         "client": "tsx scripts/cli.ts client"
     },
     "dependencies": {
+        "@standard-schema/spec": "^1.0.0",
+        "@standard-schema/utils": "^0.3.0",
+        "@standard-community/standard-json": "^0.3.5",
         "ajv": "^8.17.1",
         "ajv-formats": "^3.0.1",
         "content-type": "^1.0.5",
@@ -93,15 +96,11 @@
         "zod-to-json-schema": "^3.25.0"
     },
     "peerDependencies": {
-        "@cfworker/json-schema": "^4.1.1",
-        "zod": "^3.25 || ^4.0"
+        "@cfworker/json-schema": "^4.1.1"
     },
     "peerDependenciesMeta": {
         "@cfworker/json-schema": {
             "optional": true
-        },
-        "zod": {
-            "optional": false
         }
     },
     "devDependencies": {
@@ -116,13 +115,15 @@
         "@types/supertest": "^6.0.2",
         "@types/ws": "^8.5.12",
         "@typescript/native-preview": "^7.0.0-dev.20251103.1",
+        "@valibot/to-json-schema": "^1.3.0",
         "eslint": "^9.8.0",
         "eslint-config-prettier": "^10.1.8",
         "prettier": "3.6.2",
         "supertest": "^7.0.0",
         "tsx": "^4.16.5",
         "typescript": "^5.5.4",
         "typescript-eslint": "^8.0.0",
+        "valibot": "^1.1.0",
         "vitest": "^4.0.8",
         "ws": "^8.18.0"
     },