How to Build a Secure Serverless Endpoint for Claude's Function Calls Using AWS

When deploying Claude's function-calling feature in production, teams often default to AWS Lambda URLs, which lack critical security and versioning capabilities. API Gateway combined with Lambda offers a more robust alternative, providing built-in JWT authentication, per-stage throttling, detailed observability, and automatic CORS handling. A common pitfall involves REST API Gateway's non-proxy integration mode, which silently strips nested JSON from Claude's request payload, making debugging difficult. Enabling Lambda proxy integration ensures the full request body is forwarded correctly to the Lambda function. Adding TypeScript type safety via Zod schemas further strengthens the setup by validating request shapes at both runtime and compile time.