Serve OpenAPI to agents

When the upstream API has OpenAPI 3 or Google Discovery JSON, the gateway can serve a filtered agent-facing document at /openapi.json.

Agent summary

• The served document only describes endpoints listed in endpoints[].
• Base URLs are rewritten to the gateway.
• Upstream auth metadata is stripped because the gateway handles upstream credentials.
• Use --public-url behind reverse proxies that alter host headers.

Start with OpenAPI

pay server start provider.yml --openapi openapi.json

Override public URL

pay server start provider.yml \
  --openapi openapi.json \
  --public-url https://gateway.example.com