# API Design Principles

> Curated guidance and documentation for Large Language Models

## Pages

- [Public API Agent-Readiness Index — API Design Principles](https://apidesignprinciples.com/benchmarks/): An independent index of widely-used public APIs scored for agent-readiness on a transparent, versioned rubric. Updated quarterly.
- [API Agent-Readiness Checker — API Design Principles](https://apidesignprinciples.com/checker/): Upload an OpenAPI spec or paste a URL and get an independent agent-readiness score, grade, and the top fixes in seconds. Free for public scans.
- [API Design Principles — for the agent era](https://apidesignprinciples.com/): Ten principles for designing APIs that developers and AI agents can use — and a free checker that grades your OpenAPI spec against every one. Vendor-neutral, with a published methodology.
- [OpenAPI → MCP: a practical guide — API Design Principles](https://apidesignprinciples.com/learn/openapi-to-mcp/): How to turn an existing OpenAPI spec into something an AI agent can use safely — without rewriting your API.
- [Learn — Agent-Ready API Design Guides — API Design Principles](https://apidesignprinciples.com/learn/): Practical, vendor-neutral guides on designing APIs for AI agents: OpenAPI quality, MCP readiness, and agent-safe governance.
- [Pricing — API Design Principles](https://apidesignprinciples.com/pricing/): The agent-readiness checker is free for public scans. Paid tiers (private scans, CI, dashboards, governance) arrive in the SaaS stage.
- [The 10 API Design Principles for the agent era — API Design Principles](https://apidesignprinciples.com/principles/): Ten principles for designing APIs that developers and AI agents can use: discoverable, safely scoped, and reliable. Each one is scored by the free Agent-Readiness Checker.
- [Solutions by team — API Design Principles](https://apidesignprinciples.com/solutions/): Agent-readiness for the teams that own APIs: platform, SaaS, DevRel, AI platform, enterprise governance, and engineering leadership.