# PCH II Inference & Data

> Pay-per-call AI inference and data for autonomous agents. Payment is x402: USDC on Base (eip155:8453), one signed EIP-3009 authorization per call. No accounts, no API keys, no KYC. Discoverable in Coinbase Bazaar.

Every endpoint answers an unpaid request with HTTP 402 and a machine-readable price and output schema. To pay, resend the same request with an `X-PAYMENT` header carrying a signed authorization for the quoted amount. Prices are flat and posted; there is no negotiation or tiering.

## Endpoints
- [pch-fast](https://pathcoursehealth.com/v1/chat/completions): Instruction-tuned mixture-of-experts model for high-volume work: classification, extraction, summarisation, routing and short chat. Chosen when throughput and cost matter more than depth of reasoning. OpenAI-compatible; streaming supported. 0.002 USDC/call
- [pch-pro](https://pathcoursehealth.com/v1/chat/completions/pro): Higher-capability reasoning model for multi-step analysis, code generation, tool-use planning and long-form output. Chosen when answer quality matters more than cost per call; accepts a larger output budget than the fast tier. OpenAI-compatible; streaming supported. 0.012 USDC/call

## Discovery
- [Agent card](https://pathcoursehealth.com/.well-known/agent.json): the complete card — services, payment, terms, acceptable use, privacy, routing terms. Also served at /.well-known/agent-card.json for A2A clients.
- [x402 catalog](https://pathcoursehealth.com/.well-known/x402): machine-readable SKU list with current prices
- [OpenAPI](https://pathcoursehealth.com/openapi.json): request/response shapes

Prices are authoritative in the live HTTP 402 challenge for each endpoint.