100 API-First Products resources for developers

The standard for defining RESTful interfaces. Use 3.1 specifically for better JSON Schema compatibility and webhooks support.

An open-source alternative to Swagger UI that generates interactive documentation from OpenAPI specs with built-in API clients.

A JSON/YAML linter to enforce API design rules (e.g., camelCase for properties, mandatory 400 error responses) during CI.

A toolchain that takes an OpenAPI spec and generates idiomatic SDKs for TypeScript, Python, Java, and Go, plus a documentation site.

Ideal for end-to-end typesafe APIs where both the client and server are TypeScript-based, eliminating the need for manual schema definitions.

A TypeScript library that allows you to generate OpenAPI documentation directly from your Zod schemas to ensure code-doc parity.

A documentation platform that parses code and OpenAPI specs to create high-performance, developer-friendly documentation portals.

Use Prism to turn your OpenAPI file into a mock server locally so frontend teams can develop against an API before it's built.

An ultra-fast web framework for Edge environments (Cloudflare Workers, Bun) that provides built-in support for TypeScript and JSX.

Leverage Pydantic V2 in FastAPI for high-performance data validation and automatic generation of interactive Swagger/ReDoc pages.

Open-source API key management infrastructure that handles generation, verification, and rate-limiting at the edge.

An API Gateway designed for developers that handles authentication, rate limiting, and documentation with git-based workflows.

Implement global rate limits at the edge using the `rate-limit` binding to protect your origin from abuse and DDoS.

A webhooks-as-a-service provider that handles the infrastructure for sending, retrying, and monitoring outbound webhooks to your users.

Use Upstash's serverless Redis and `@upstash/ratelimit` library for low-latency sliding window rate limiting across serverless functions.

Use Clerk to manage machine-to-machine (M2M) authentication and provide your users with a dashboard to manage their own API keys.

Expose a JSON Web Key Set (JWKS) endpoint to allow your customers to verify the authenticity of your signed JWTs or webhooks.

Follow the Standard Webhooks specification for payload signing and headers to ensure compatibility with modern consumer libraries.

An open-source tool for intercepting and inspecting TLS traffic, useful for debugging complex API-to-API communication.

An open-source alternative to Postman for testing and sharing API request collections within your engineering team.

Integrate Stripe's metered billing to charge customers based on the number of API calls processed in a billing cycle.

An open-source metering and billing engine that acts as an alternative to Stripe for complex usage-based pricing models.

A specialized analytics tool that tracks API usage per user/key, providing insights into which endpoints are most valuable.

An observability platform specifically for AI API wrappers, tracking LLM costs, latency, and token usage for OpenAI/Anthropic proxies.

A high-scale usage-based billing platform designed specifically for API-first companies with complex contract terms.

Use Propel to build usage dashboards for your users so they can see their own API consumption and costs in real-time.

Use Inngest to queue and retry external API calls or webhooks with built-in backoff logic and concurrency control.

Implement OTel instrumentation in your API to track requests across microservices and identify performance bottlenecks.

Use PostHog to manage feature rollout to specific API consumers based on their account ID or subscription tier.

Deploy ClickHouse to store and query billions of API request logs for internal auditing and billing calculations.