ExpressJS MCP

# Example 02: Full Schema Description This example demonstrates how to provide detailed schema information for MCP tools using Zod schemas. ## Features - **Zod Schema Validation**: Automatic input/output validation - **Rich Type Information**: Detailed schemas for MCP clients - **Examples**: Provide usage examples for each tool - **Better Error Messages**: Schema validation errors are descriptive ## Running the Example ```bash # Install dependencies pnpm install # Run the example pnpm tsx examples/02-full-schema/server.ts ``` ## Schema Annotations This example uses `schemaAnnotations` to provide: 1. **Input Schema**: Validates incoming arguments 2. **Output Schema**: Validates response data 3. **Description**: Human-readable tool description 4. **Examples**: Sample inputs for documentation ```typescript const schemaAnnotations = { "GET /items": { description: "List all items with pagination", input: ListItemsQuerySchema, output: ItemsListResponseSchema, examples: [{ skip: 0, limit: 10 }], }, // ... more routes }; ``` ## Testing with Schema Validation 1. **Valid Request** - Works as expected: ```bash curl -X POST http://localhost:3002/mcp/invoke \ -H "Content-Type: application/json" \ -d '{ "toolName": "POST_/items", "args": { "name": "Valid Item", "price": 29.99, "tags": ["test"] } }' ``` 2. **Invalid Request** - Schema validation error: ```bash curl -X POST http://localhost:3002/mcp/invoke \ -H "Content-Type: application/json" \ -d '{ "toolName": "POST_/items", "args": { "name": "", "price": -10 } }' ``` The invalid request will return a validation error with details about what's wrong. ## Benefits of Schema Annotations 1. **Type Safety**: Ensures data conforms to expected shapes 2. **Auto-documentation**: Schemas serve as API documentation 3. **Client Generation**: MCP clients can generate typed interfaces 4. **Error Prevention**: Catches issues before they reach business logic ## Zod Integration The example uses [Zod](https://zod.dev) for schema definition: ```typescript const ItemSchema = z.object({ id: z.number().int().positive(), name: z.string().min(1), price: z.number().positive(), tags: z.array(z.string()).default([]), }); ``` Zod schemas are automatically converted to JSON Schema for MCP tools. ## Next Steps - See [Example 03](../03-custom-endpoints) for selective route exposure - See [Example 04](../04-separate-server) for standalone MCP server - See [Example 07](../07-timeout) for timeout configuration