The Idempotency Fingerprint API from WritersLogic Verifiable AI Agent Hub — 1 operation(s) for idempotency fingerprint.
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openapi: 3.2.0
info:
title: WritersLogic Verifiable AI Agent Hub Idempotency…
version: 2.0.0
description: Pay-per-call agents settled in USDC on Base via x402. Every response carries a signed provenance envelope.
contact:
name: WritersLogic
url: https://writerslogic.com/agents
email: agents@writerslogic.com
servers:
- url: https://agents.writerslogic.com
tags:
- name: Idempotency Fingerprint
paths:
/api/v1/idempotency-fingerprint:
post:
operationId: idempotency_fingerprint
summary: Derive a stable idempotency fingerprint from declared identity fields and flag…
description: 'Hashes the fields you declare as the identity of an operation (JSON Pointers into each request) with RFC 8785 canonical JSON and SHA-256, so retries of the same operation get the same fingerprint regardless of key order, and flags the ways that breaks: an identity field missing, an identity field also declared volatile, identity values that look like timestamps, epoch times or UUIDs (heuristic), and undeclared fields that differ between attempts. For an agent that must choose an Idempotency-Key for a retried write. Does not know any provider''s key rules, length limits or scope, and does not send anything.
Price: 0.005 USDC on Base (x402).'
x-x402-price-usdc: '0.005'
x-x402-amount: '5000'
x-payment-info:
protocols:
- x402
price:
mode: fixed
currency: USD
amount: '0.005'
x-audience: agent-infra
x-sample-url: https://agents.writerslogic.com/api/v1/samples/idempotency-fingerprint
security:
- x402: []
- apiKey: []
requestBody:
required: true
content:
application/json:
schema:
type: object
additionalProperties: false
required:
- requests
- identity
properties:
requests:
type: array
minItems: 1
maxItems: 20
items:
description: A request (body, or {method,url,body}) as JSON; several attempts of the same intended operation.
identity:
type: array
minItems: 1
maxItems: 50
items:
type: string
maxLength: 300
description: JSON Pointers whose values define the operation's identity.
volatile:
type: array
maxItems: 50
items:
type: string
maxLength: 300
description: JSON Pointers declared to change per attempt (timestamps, nonces, request ids).
scope:
type: string
maxLength: 200
description: Mixed into the hash (for example operation name and tenant) so equal bodies in different scopes get different fingerprints.
example:
requests:
- amount: 500
currency: USD
customer: c_1
sentAt: '2026-11-04T10:00:00Z'
- amount: 500
currency: USD
customer: c_1
sentAt: '2026-11-04T10:00:07Z'
identity:
- /amount
- /currency
- /customer
volatile:
- /sentAt
scope: charge:acct_9
responses:
'200':
description: Paid result with provenance
content:
application/json:
schema:
type: object
properties:
data:
type: object
properties:
status:
type: string
enum:
- pass
- fail
- unknown
- unsupported
description: '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.'
fingerprints:
type: array
items:
type: string
description: Hex SHA-256.
stable:
type: boolean
description: All requests produce the same fingerprint.
undeclaredDifferences:
type: array
items:
type: string
description: Pointers of leaf values that differ across requests and are neither identity nor volatile.
derivation:
type: string
witnesses:
type: array
items:
type: object
properties:
ruleId:
type: string
detail:
type: string
path:
type: string
description: JSON pointer or dotted path into the input.
offset:
type: integer
index:
type: integer
expected:
description: What the rule required.
actual:
description: What the input had.
versions:
type: object
description: Every semantic dependency of this answer (engine, tables and their as-of dates, tokenizer, calendar, rounding profile).
limits:
type: array
items:
type: string
deterministic:
type: boolean
description: 'Always true: pure code, no model.'
_provenance:
type: object
description: C2PA-aligned manifest and W3C VC 2.0 (eddsa-jcs-2022) issued by the hub DID; verify at POST /api/v1/verify-provenance
required:
- data
- _provenance
'400':
description: Invalid request (no payment consumed)
content:
application/json:
schema:
type: object
properties:
error:
type: string
code:
type: string
'401':
description: Invalid X-API-KEY
content:
application/json:
schema:
type: object
properties:
error:
type: string
code:
type: string
'402':
description: Payment required or invalid
content:
application/json:
schema:
type: object
description: x402 v2 PaymentRequired (also base64 in the PAYMENT-REQUIRED header)
properties:
x402Version:
type: integer
error:
type: string
code:
type: string
resource:
type: object
accepts:
type: array
items:
type: object
extensions:
type: object
'502':
description: Upstream failure; the payment is released or not settled
content:
application/json:
schema:
type: object
properties:
error:
type: string
code:
type: string
tags:
- Idempotency Fingerprint
components:
securitySchemes:
x402:
type: apiKey
in: header
name: PAYMENT-SIGNATURE
description: x402 v2 payment payload (base64) sent after a 402 challenge
apiKey:
type: apiKey
in: header
name: X-API-KEY