The Invoice Audit API from WritersLogic Verifiable AI Agent Hub — 1 operation(s) for invoice audit.
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openapi: 3.2.0
info:
title: WritersLogic Verifiable AI Agent Hub Invoice Audit API
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: Invoice Audit
paths:
/api/v1/invoice-audit:
post:
operationId: invoice_audit
summary: 'Invoice arithmetic audit: line extensions, discounts, supplied tax, totals…'
description: 'Recomputes up to 500 invoice lines in exact decimal arithmetic and compares them with the stated amounts, for an agent about to approve, pay or reconcile an invoice. Checks: quantity x unit price less discount equals the line amount; tax is taken as supplied (tax amounts are summed, never looked up) and, where a rate is given, tax equals rate x line amount under the declared rounding scope (per line, or per rate on the invoice); subtotal, discount total, tax total and grand total equal the sums. Each mismatch names the JSON path, the rule, the expected and actual minor units and the signed drift. Does not decide tax rates or jurisdictions, does not check vendor identity or purchase-order terms, and totals not stated are not checked.
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: business
x-sample-url: https://agents.writerslogic.com/api/v1/samples/invoice-audit
security:
- x402: []
- apiKey: []
requestBody:
required: true
content:
application/json:
schema:
type: object
additionalProperties: false
required:
- lines
properties:
lines:
type: array
minItems: 1
maxItems: 500
items:
type: object
required:
- quantity
- unitPrice
- amount
properties:
id:
type: string
maxLength: 80
quantity:
type: string
pattern: ^-?\d{1,15}(\.\d{1,12})?$
maxLength: 30
description: 'Decimal string such as "-12.50" (up to 15 integer and 12 fraction digits). JSON numbers are not accepted: they are binary floats.'
unitPrice:
type: string
pattern: ^-?\d{1,15}(\.\d{1,12})?$
maxLength: 30
description: Price per unit in major units; sub-cent precision allowed.
amount:
type: string
pattern: ^-?\d{1,15}(\.\d{1,12})?$
maxLength: 30
description: Stated net line amount after the line discount.
discount:
type: string
pattern: ^-?\d{1,15}(\.\d{1,12})?$
maxLength: 30
description: Line discount as a positive amount in major units.
taxRate:
type: string
pattern: ^-?\d{1,15}(\.\d{1,12})?$
maxLength: 30
description: 'Tax rate in percent, e.g. "7.5". With taxAmount it is checked. A non-zero rate without taxAmount cannot be checked: the result is unknown, and no tax is inferred.'
taxAmount:
type: string
pattern: ^-?\d{1,15}(\.\d{1,12})?$
maxLength: 30
description: Tax on this line as supplied.
additionalProperties: false
stated:
type: object
properties:
subtotal:
type: string
pattern: ^-?\d{1,15}(\.\d{1,12})?$
maxLength: 30
description: 'Decimal string such as "-12.50" (up to 15 integer and 12 fraction digits). JSON numbers are not accepted: they are binary floats.'
discountTotal:
type: string
pattern: ^-?\d{1,15}(\.\d{1,12})?$
maxLength: 30
description: Sum of line discounts.
taxTotal:
type: string
pattern: ^-?\d{1,15}(\.\d{1,12})?$
maxLength: 30
description: 'Decimal string such as "-12.50" (up to 15 integer and 12 fraction digits). JSON numbers are not accepted: they are binary floats.'
total:
type: string
pattern: ^-?\d{1,15}(\.\d{1,12})?$
maxLength: 30
description: Grand total; checked against subtotal + taxTotal.
additionalProperties: false
currency:
type: string
pattern: ^[A-Z]{3}$
description: ISO 4217 alphabetic code, upper case.
exponent:
type: integer
minimum: 0
maximum: 8
rounding:
type: string
enum:
- half-up
- half-down
- half-even
- up
- down
- ceiling
- floor
description: 'Default half-up. half-up: ties away from zero. half-down: ties toward zero. half-even: ties to the even neighbour. up: away from zero. down: toward zero. ceiling: toward +infinity. floor: toward -infinity.'
taxRounding:
type: string
enum:
- line
- invoice
description: 'line (default): each line''s tax is rounded on its own. invoice: tax is rounded once per distinct rate on the sum of the line amounts, and compared with the supplied tax sum for that rate.'
toleranceMinor:
type: integer
minimum: 0
maximum: 1000
description: Largest absolute drift in minor units still treated as a match. Default 0.
example:
currency: USD
lines:
- id: A
quantity: '3'
unitPrice: '19.99'
amount: '59.97'
taxRate: '8'
taxAmount: '4.80'
- id: B
quantity: '2'
unitPrice: '5.005'
amount: '10.01'
taxRate: '8'
taxAmount: '0.80'
stated:
subtotal: '69.98'
taxTotal: '5.60'
total: '75.58'
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.'
mismatches:
type: array
items:
type: object
properties:
path:
type: string
rule:
type: string
expectedMinor:
type: integer
actualMinor:
type: integer
driftMinor:
type: integer
description: actual minus expected.
description: Integers are exact below 10^15 minor units; a mismatch beyond that is reported only as a minor-out-of-range witness carrying exact decimal strings.
checksRun:
type: array
items:
type: string
computed:
type: object
properties:
subtotal:
type: string
discountTotal:
type: string
taxTotal:
type: string
total:
type: string
exponent:
type: integer
netDriftMinor:
type: integer
description: Sum of signed drifts over all mismatches; absent when the sum is beyond 10^15 minor units (a minor-out-of-range witness carries it as a 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:
- Invoice Audit
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