Missive — API testing as Markdown

Missive is an agent skill for exercising and verifying running APIs from plain Markdown. Each collection is a human-readable *.api.md file you can read, diff, and commit. Graphical API clients do three small things at their core — describe HTTP requests, hold the secrets those requests need, and fire them; the GUI, the account shell, and the sync engine are the weight. Missive keeps the essence and drops the binary: secrets stay in a local vault, referenced by the file but never stored in it, and your coding agent is the engine that reads the folder, resolves the secrets out-of-band, and reasons about the responses. It’s the Ephemera pattern — auditable Markdown plus an agent, no binary tooling — pointed at the behavioral half of the API lifecycle. Where Ephemera provisions infrastructure and verifies it exists, Missive exercises a running API and verifies it behaves.

• One .api.md file per collection — readable, diffable, committable
• A living Notebook per endpoint — gotchas hit, last response shape, schema drift observed over time, not just the request’s shape
• Three reference types — {{env}}, {{var:NAME}}, {{vault:NAME}} — so secrets live in a local vault, never in the file or the diff
• Inject-and-fire, never bare-read — a secret enters a single subprocess at fire-time; only the response is captured
• One artifact, three modes — Run fires, Check asserts, Mock serves canned responses; agent-driven in v1, an AI-free CI runner in v1.1

This page is the readable overview — Missive now has its own home at missive.daystra.com. Open it there or get in touch.