mcp-builder

Build an MCP server by implementing tools with structured input validation using Pydantic (Python) or Zod (TypeScript), following snake_case naming conventions. Use FastMCP for Python or the Node MCP SDK for TypeScript, configure your chosen transport (stdio, SSE, or HTTP), and register tools with consistent response formats and character limits to enable Claude to invoke external services.

Both FastMCP (Python) and Node/TypeScript MCP implementations support the same core MCP protocol and transports. Choose Python for rapid prototyping with Pydantic validation, or TypeScript for type safety and ecosystem integration. The choice depends on your existing stack; both enforce identical best practices for tool naming, error handling, and pagination.

Validate tool inputs using Pydantic schemas in Python or Zod in TypeScript before processing. Define strict input schemas for each tool, enforce type checking, and return clear error messages when validation fails. This ensures Claude receives predictable responses and prevents malformed requests from reaching external APIs.

Yes, MCP servers support multiple transports—stdio, SSE, and HTTP. Configure the transport layer during server initialization to match your deployment environment. Stdio works for local integrations, SSE and HTTP enable remote Claude connections. All transports enforce the same tool registration and response format standards.

MCP servers must implement error handling that catches failures from external API calls and returns structured error responses to Claude within character limits. Use try-catch blocks, implement timeouts, and return descriptive error messages so Claude can retry, fall back, or inform the user of the failure.

Implement pagination by accepting limit and offset parameters in tool inputs, validated via Pydantic or Zod schemas. Return paginated results with metadata indicating total count and whether more results exist. This lets Claude iteratively fetch large datasets while respecting API rate limits and response size constraints.