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MCP TypeScript SDK (v1)

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MCP TypeScript SDK / validation

validation ​

JSON Schema validation

This module provides configurable JSON Schema validation for the MCP SDK. Choose a validator based on your runtime environment:

  • AjvJsonSchemaValidator: Best for Node.js (default, fastest) Import from: @modelcontextprotocol/sdk/validation/ajv Requires peer dependencies: ajv, ajv-formats

  • CfWorkerJsonSchemaValidator: Best for edge runtimes Import from: @modelcontextprotocol/sdk/validation/cfworker Requires peer dependency: @cfworker/json-schema

Example ​

typescript
// For Node.js with AJV
import { AjvJsonSchemaValidator } from '@modelcontextprotocol/sdk/validation/ajv';
const validator = new AjvJsonSchemaValidator();

// For Cloudflare Workers
import { CfWorkerJsonSchemaValidator } from '@modelcontextprotocol/sdk/validation/cfworker';
const validator = new CfWorkerJsonSchemaValidator();

Interfaces ​

jsonSchemaValidator ​

Defined in: src/validation/types.ts:55

Provider interface for creating validators from JSON Schemas

This is the main extension point for custom validator implementations. Implementations should:

  • Support JSON Schema Draft 2020-12 (or be compatible with it)
  • Return validator functions that can be called multiple times
  • Handle schema compilation/caching internally
  • Provide clear error messages on validation failure

Example ​

typescript
class MyValidatorProvider implements jsonSchemaValidator {
  getValidator<T>(schema: JsonSchemaType<T>): JsonSchemaValidator<T> {
    // Compile/cache validator from schema
    return (input: unknown) => {
      // Validate input against schema
      if (valid) {
        return { valid: true, data: input as T, errorMessage: undefined };
      } else {
        return { valid: false, data: undefined, errorMessage: 'Error details' };
      }
    };
  }
}

Methods ​

getValidator() ​

getValidator<T>(schema): JsonSchemaValidator<T>

Defined in: src/validation/types.ts:62

Create a validator for the given JSON Schema

Type Parameters ​
T ​

T

Parameters ​
schema ​

JsonSchemaType

Standard JSON Schema object

Returns ​

JsonSchemaValidator<T>

A validator function that can be called multiple times

Type Aliases ​

JsonSchemaType ​

JsonSchemaType = JSONSchema.Interface

Defined in: src/validation/types.ts:14

JSON Schema type definition (JSON Schema Draft 2020-12)

This uses the object form of JSON Schema (excluding boolean schemas). While true and false are valid JSON Schemas, this SDK uses the object form for practical type safety.

Re-exported from json-schema-typed for convenience.

See ​

https://json-schema.org/draft/2020-12/json-schema-core.html

JsonSchemaValidator ​

JsonSchemaValidator<T> = (input) => JsonSchemaValidatorResult<T>

Defined in: src/validation/types.ts:26

A validator function that validates data against a JSON Schema

Type Parameters ​

T ​

T

Parameters ​

input ​

unknown

Returns ​

JsonSchemaValidatorResult<T>

JsonSchemaValidatorResult ​

JsonSchemaValidatorResult<T> = { data: T; errorMessage: undefined; valid: true; } | { data: undefined; errorMessage: string; valid: false; }

Defined in: src/validation/types.ts:19

Result of a JSON Schema validation operation

Type Parameters ​

T ​

T