The Font Coverage API from WritersLogic Verifiable AI Agent Hub — 1 operation(s) for font coverage.
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openapi: 3.2.0
info:
title: WritersLogic Verifiable AI Agent Hub Font Coverage 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: Font Coverage
paths:
/api/v1/font-coverage:
post:
operationId: font_coverage
summary: 'Font coverage: does this font have glyphs for this text, and does it fit the box'
description: 'Reads a TrueType or OpenType font you supply as base64 (up to 2 MB) and a text of up to 5000 characters, for an agent about to render text in a fixed font: lists every code point with no glyph in the cmap (formats 4 and 12) and sums the hmtx advance widths to test a width in pixels. Every offset is bounds-checked. It does not apply kerning, ligatures or shaping (combining marks and complex scripts make the width check unknown), does not read WOFF, WOFF2 or font collections (unsupported), and does not render the font.
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/font-coverage
security:
- x402: []
- apiKey: []
requestBody:
required: true
content:
application/json:
schema:
type: object
additionalProperties: false
required:
- fontBase64
- text
properties:
fontBase64:
type: string
minLength: 8
maxLength: 2796204
description: Base64 of a .ttf or .otf file (sfnt, not WOFF).
text:
type: string
minLength: 1
maxLength: 5000
fontSizePx:
type: number
minimum: 1
maximum: 2000
description: Needed for a width check.
maxWidthPx:
type: number
minimum: 0
maximum: 100000
description: Box width; the widest line (split on \n) must fit.
example:
fontBase64: AAEAAAAFAAAAAAAAY21hcAAAAAAAAABcAAAARGhlYWQAAAAAAAAAoAAAADZoaGVhAAAAAAAAANgAAAAkaG10eAAAAAAAAAD8AAAAFG1heHAAAAAAAAABEAAAAAYAAAABAAMAAQAAAAwABAA4AAAACgAAAAAAAABBAEIAQwDp//8AAABBAEIAQwDp////wP/A/8D/GwABAAAAAAAAAAAAAAABAAAAAQAAAAAAAF8PPPUAAAPoAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAEAAAMg/zgAWgAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFAfQAAAJYAAACvAAAAyAAAAImAAAAAFAAAAUAAA==
text: ABC é
fontSizePx: 10
maxWidthPx: 100
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.'
font:
anyOf:
- type: object
properties:
kind:
type: string
unitsPerEm:
type: integer
glyphCount:
type: integer
ascender:
type: integer
descender:
type: integer
lineGap:
type: integer
cmap:
type: object
properties:
platformId:
type: integer
encodingId:
type: integer
format:
type: integer
- type: 'null'
requestedCodePoints:
type: integer
description: Distinct non-newline code points in the text.
coveredCodePoints:
type: integer
missing:
type: array
items:
type: object
properties:
codePoint:
type: string
char:
type: string
offset:
type: integer
description: UTF-16 offset of the first occurrence.
missingTruncated:
type: boolean
width:
anyOf:
- type: object
properties:
lines:
type: integer
widestLineUnits:
type: integer
widestLinePx:
anyOf:
- type: number
- type: 'null'
maxWidthPx:
anyOf:
- type: number
- type: 'null'
- type: 'null'
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:
- Font Coverage
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