You cancelled the run - did the work actually stop? This service re-probes each dispatched leg's downstream state and receipts the answer, per leg: stopped, landed before the cancel, still running, or honestly unknown.
MCP cancellation is a notification, not a request: the specification forbids a response, receivers only SHOULD stop and MAY ignore the signal, and frameworks offer no hard-stop API - so after every timeout, user Stop, and budget halt, the operator is forced to decide blind: re-issue (risking a duplicate effect if the first leg actually landed) or move on (risking the cancelled work completing unwanted). This service closes that moment. Submit the cancel record and it actively re-probes each leg's downstream state on servers you do not control - status and idempotency surfaces, resource state, task/status surfaces where they exist - and returns an HMAC-signed receipt with a per-leg four-state verdict: STOPPED-CONFIRMED, LANDED-BEFORE-CANCEL (with the effect evidence and its timing graded against the cancel timestamp), STILL-RUNNING (re-probed a bounded number of times before the receipt issues), or UNKNOWN - a first-class signed verdict naming the probe attempted and its cause, never folded into STOPPED. Corroboration never rides the request: probes resolve only against a server-side registry populated out-of-band, and caller fields claiming a verdict are stripped. Every receipt names the probe class used per leg, so routing is auditable.
1. POST /register (no auth) with {"name": "your-operator", "wallet": "0x..."} - returns your account_id and a bearer token shown once. 2. An admin onboards downstream targets into the server-side registry out-of-band (support@textforagents.com). 3. POST /verify with your token and a cancel record {{"cancel_id", "cancel_ts", "legs": [{{"leg_id","request_id","target_id"}}]}} - one leg is a $0.01 verdict; more than one leg is a $4.99 full cancel audit (your first audit is the one-time free trial). Pay via the x402 challenge (X-PAYMENT header, Base USDC, payTo raw 0x), or POST /subscribe for a plan. 4. POST /receipt/verify checks any receipt's HMAC signature. MCP: POST /mcp (initialize, tools/list, tools/call verify_cancel).
Stated plainly, because the lab proved the boundaries: UNKNOWN is a first-class signed verdict, never folded into STOPPED - a leg with no decidable surface can only ever return UNKNOWN; real-server probe coverage and the real-world UNKNOWN rate are unmeasured - the mechanism is proven against simulators modelling the documented shapes, not live third-party servers; deep-probe legs are quoted exactly, never silently absorbed into the simple-probe price (deep legs exact-quote only); willingness to pay is unmeasured - nobody has sold this verdict before.
Support: support@textforagents.com