Idempotency registry: has key K already been done? Claim it, complete it, read the stored result

$0.005 USDC per call · Agent infrastructure · POST /api/v1/idempotency-registry · Id idempotency-registry

Shared memory for side-effecting operations across agents and retries. begin(key) answers proceed (you hold a short claim), wait (another owner is mid-flight), already_completed (returns the stored result pointer), or fingerprint_mismatch (same key, different operation). complete(key) records the result pointer; abandon(key) lets someone retry. The claim expires, so a crashed worker does not block the key forever. Never infers completion from a timeout: only complete() marks a key done.

What you get

A duplicate charge, email or order costs far more than one $0.005 check before the side effect.

Call it

Send the JSON body below to https://agents.writerslogic.com/api/v1/idempotency-registry. An unpaid request answers 402 with the price and how to pay; a request that fails with a 5xx status is not charged.

curl -i -X POST https://agents.writerslogic.com/api/v1/idempotency-registry \
  -H 'content-type: application/json' \
  -d '{"op":"begin","key":"refund:ch_3Q1:2026-11-04","owner":"billing-agent-2","fingerprint":"sha256:4be1…","requestId":"ba2-refund-ch_3Q1"}'

Input

Field	Type	Required	Description
`op`	string; one of "begin", "complete", "abandon", "get"	yes
`key`	string	yes	Idempotency key, e.g. refund:ch_123:2026-11-04.
`owner`	string; length 1..128	no	Worker id; required for begin, complete and abandon.
`fingerprint`	string; length 1..128	no	Hash of the operation's identity fields; a later begin with a different fingerprint is refused.
`claimSeconds`	integer; 1..3600	no	How long a begin claim lasts; default 300.
`retentionHours`	integer; 1..168	no	How long a completed key is remembered; default 24.
`result`	object	no	complete: where the outcome lives (do not store payloads here).
`tenantId`	string	no	Required for API-key callers (namespaced as key:<tenantId>; keep it unguessable). Ignored when a wallet paid: the payer address is the tenant.
`requestId`	string	no	Caller-chosen id for this mutation. A retry with the same id and same input returns the stored response (24 h) instead of applying twice; the same id with different input is rejected. Send one on every mutation you may retry: without it a retry is applied again (fleet-memory record appends a duplicate; a repeated spend-ledger commit or release answers NO_HOLD because the first call already took effect).

Example request body

{
  "op": "begin",
  "key": "refund:ch_3Q1:2026-11-04",
  "owner": "billing-agent-2",
  "fingerprint": "sha256:4be1…",
  "requestId": "ba2-refund-ch_3Q1"
}

Result

The response is { "data": ..., "_provenance": ... }. data carries these fields; _provenance is a signed W3C Verifiable Credential with a C2PA-style manifest, checked free at POST /api/v1/verify-provenance.

Field	Type	Required	Description
`status`	string; one of "pass", "fail", "unknown", "unsupported"	no	pass: every rule held. fail: a rule was violated (see witnesses). unknown: the input lacks the evidence to decide. unsupported: outside what this engine covers. Missing evidence is never a pass.
`op`	string	no
`decision`	string; one of "proceed", "wait", "already_completed", "fingerprint_mismatch", "recorded", "not_owner", "none"	no
`state`	one of	no	in_progress, completed, abandoned, or null when the key is unknown.
`owner`	one of	no
`claimExpiresAt`	one of	no
`completedAt`	one of	no
`stored`	one of	no	The result recorded by complete().
`witnesses`	array<object>	no
`versions`	object	no	Every semantic dependency of this answer (engine, tables and their as-of dates, tokenizer, calendar, rounding profile).
`limits`	array<string>	no
`deterministic`	boolean	no	Always true: pure code, no model.

Pay and connect

Available through: x402 (USDC on Base), MCP. MCP clients reach it through the agent-coordination-kit package.

Machine-readable

This agent as JSON (schemas, example, OpenAPI operation)
Free signed sample response
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