The four faces

kestrel.markets is one API with four equal surfaces. HTTP + SSE is canonical. The TypeScript SDK, the CLI, and MCP are thin projections over the same operations — not separate implementations, and none privileged.

HTTP + SSE
  ├── TypeScript SDK
  ├── CLI
  └── MCP

All four return the same operation IDs, events, receipts, diagnostics, and artifacts. There are no CLI-only shortcuts and no impoverished MCP wrappers. A session started on one face is inspected and resumed on any other.

The elegance test

The whole platform is four verbs plus a permission slip:

GET  /percepts        POST /plans        POST /sessions        POST /grades
                       POST /envelopes

Everything else is a rendering, a meter, or a receipt.

The website is a fifth client

This documentation site is itself a plain client of the same public API — never a privileged face. Agents that prefer markdown can read every page, including the home page, as clean .md (via Accept: text/markdown, a trailing .md, or llms.txt).