The Metered Price API from WritersLogic Verifiable AI Agent Hub — 1 operation(s) for metered price.
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openapi: 3.2.0
info:
title: WritersLogic Verifiable AI Agent Hub Metered Price 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: Metered Price
paths:
/api/v1/metered-price:
post:
operationId: metered_price
summary: 'Tiered usage pricing: graduated or volume tiers, included quantity, package…'
description: 'Prices a usage quantity against up to 50 tiers, graduated (each tier prices only its own units) or volume (the tier holding the whole quantity prices all of it), for an agent checking a usage bill or quoting a plan. Order of operations: subtract the included quantity, convert to billing packages (per N units, rounded up, down or not at all), price the tiers, add flat fees, apply the minimum charge, round once to the currency''s minor unit. Tier `upTo` bounds are inclusive and strictly ascending; only the last tier may omit it. Unit prices may carry sub-cent precision. A quantity above the last bounded tier fails. Flat fees apply when a tier holds units (graduated) or is the matching tier (volume) and quantity is above zero. Does not meter usage or apply tax.
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/metered-price
security:
- x402: []
- apiKey: []
requestBody:
required: true
content:
application/json:
schema:
type: object
additionalProperties: false
required:
- quantity
- mode
- tiers
properties:
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.'
mode:
type: string
enum:
- graduated
- volume
tiers:
type: array
minItems: 1
maxItems: 50
items:
type: object
required:
- unitPrice
properties:
upTo:
type: string
pattern: ^-?\d{1,15}(\.\d{1,12})?$
maxLength: 30
description: Inclusive upper bound in billing units. Omit on the last tier for unlimited.
unitPrice:
type: string
pattern: ^-?\d{1,15}(\.\d{1,12})?$
maxLength: 30
description: Price per billing unit in major units; sub-cent precision allowed.
flatFee:
type: string
pattern: ^-?\d{1,15}(\.\d{1,12})?$
maxLength: 30
description: Fee in major units charged with this tier.
additionalProperties: false
included:
type: string
pattern: ^-?\d{1,15}(\.\d{1,12})?$
maxLength: 30
description: Free quantity subtracted before packaging and tiers (never below zero).
per:
type: string
pattern: ^-?\d{1,15}(\.\d{1,12})?$
maxLength: 30
description: Units per billing package (default 1). Tiers are expressed in packages.
packageRounding:
type: string
enum:
- up
- down
- none
description: How a partial package is billed when per > 1. Default up.
minimum:
type: string
pattern: ^-?\d{1,15}(\.\d{1,12})?$
maxLength: 30
description: Minimum charge in major units, applied after the tiers.
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: 'Final rounding to the minor unit. 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.'
example:
quantity: '250'
mode: graduated
tiers:
- upTo: '100'
unitPrice: '0.10'
- upTo: '1000'
unitPrice: '0.08'
- unitPrice: '0.05'
currency: USD
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.'
charge:
type: string
description: Final charge at the currency's precision.
chargeMinor:
type: integer
exponent:
type: integer
billableUnits:
type: string
description: Billing units after included quantity and packaging.
breakdown:
type: array
items:
type: object
properties:
tier:
type: integer
units:
type: string
unitPrice:
type: string
flatFee:
type: string
subtotal:
type: string
description: Unrounded; exact unless packageRounding is none and per does not divide the quantity, then rounded to 90 significant digits for display only (the charge is exact).
unroundedTotal:
type: string
minimumApplied:
type: boolean
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:
- Metered Price
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