← Back to Blog
Engineering

How to Design an API That AI Agents Actually Use

2026-05-2212 min read
# Designing APIs for AI Agents Agents consume APIs differently than humans. Understanding these differences is the key to building APIs that agents actually pay for. ## Key Design Principles ### 1. Self-Describing Schemas Every endpoint must have a complete OpenAPI 3.1 description. Agents use this schema to understand parameters, responses, and error codes before making a single call. ### 2. Predictable Error Responses Agents need structured, consistent error formats. HTTP status codes alone aren't enough — include machine-readable error codes and remediation hints. ### 3. Fast Response Times Agent workflows are often sequential. A 500ms API call in a 10-step chain means 5 seconds of latency. Target under 100ms p50. ### 4. Micro-Pricing Agents may call your API 10 times or 10,000 times. Fixed monthly plans don't work. Per-call pricing with free tiers drives adoption.