API

The web UI's hook pages are also API resources at the same URLs: ask for JSON and you get the data the page shows. A .json or .html extension picks the representation; otherwise the Accept header does, and JSON is the default. So the URL in your browser's address bar is the one to script against:

curl https://tsrelay.<your tailnet>/hooks                               # your hooks, as JSON
curl https://tsrelay.<your tailnet>/hooks/h_3k2/calls.json              # the same as the hook page's call list
curl -H 'Accept: text/event-stream' https://tsrelay.<your tailnet>/hooks  # live changes to your hooks

/ is the entry document (who you are, your limits, and links to the rest), and /hooks/{id} streams changes to one hook. The relay identifies you by your tailnet identity, so the API needs no tokens; only a public hook's URL works like one. The full description is an OpenAPI document at /openapi.json (or /openapi.yaml), which the API reference renders.

Every write (POST, PATCH, DELETE) needs Content-Type: application/json, also one without a body: browsers can't send that across sites without asking first, which keeps other sites from writing as you.

Durations you set (holdTimeout, maxHookTtl) are Go duration strings such as 30s; what 0s means depends on the setting, as Compatibility lists. Timestamps are RFC 3339 strings in UTC. Durations the relay measures (durationMs, ttfbMs, waitedForMs on calls and attempts) are JSON numbers of milliseconds with microsecond precision, so a 412 µs response reads 0.412.

Lists are objects ({"hooks": [...]}, {"calls": [...]}), so they can gain siblings later. Within a major version the API only grows: clients must ignore unknown fields, enumeration values, event types and problem codes (falling back to the HTTP status for a code they don't know), and a request field the relay doesn't know, or a query parameter a write doesn't take, is refused with 422 and the code unsupported_field. Compatibility has the full promise.

The calls endpoints are described under Inspecting calls, and the errors the API returns in the error reference.