The Llm Watermark Detector API from WritersLogic Verifiable AI Agent Hub — 1 operation(s) for llm watermark detector.
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openapi: 3.2.0
info:
title: WritersLogic Verifiable AI Agent Hub Llm Watermark Detector…
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: Llm Watermark Detector
paths:
/api/v1/llm-watermark-detector:
post:
operationId: llm_watermark_detector
summary: 'Detect LLM text watermark evidence: green-list z-test for a key you hold, plus…'
description: 'Tests whether text carries watermark evidence, for a pipeline that must decide whether to trust or label content. Two independent checks: (1) a green-list z-test (Kirchenbauer et al. 2023) over green flags you supply, or over token ids and a key using this endpoint''s own HMAC-SHA256 scheme, returning the z-score and exact binomial p-value; (2) an invisible-character scan of the text for zero-width characters, Unicode tag characters (which spell hidden ASCII), variation selectors and bidi controls, with offsets. It cannot detect a vendor watermark without that vendor''s key and tokenizer, never recovers a key, and does not remove or alter anything. A pass means no evidence at this threshold, not that the text is human-written; paraphrase can erase a statistical watermark.
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/llm-watermark-detector
security:
- x402: []
- apiKey: []
requestBody:
required: true
content:
application/json:
schema:
type: object
additionalProperties: false
required: []
properties:
text:
type: string
maxLength: 100000
minLength: 1
description: Text to scan for invisible markers.
greenFlags:
type: array
items:
type: integer
minimum: 0
maximum: 1
maxItems: 100000
description: 'One 0/1 per scored token: 1 when your own detector''s green list contains the token. Deduplicate repeated n-grams yourself if your scheme requires it.'
tokenIds:
type: array
items:
type: integer
minimum: 0
maximum: 2147483647
maxItems: 5000
description: Token ids in order (at most 5000). Green membership is computed from the key with the hmac-sha256-green-1 scheme; each distinct consecutive pair is scored once.
key:
type: string
maxLength: 256
minLength: 1
description: Secret key for tokenIds. Used for this call only and never stored or echoed.
scheme:
type: string
enum:
- hmac-sha256-green-1
description: Scheme for tokenIds; default and only value.
gamma:
type: number
minimum: 0.01
maximum: 0.99
description: Expected green fraction under no watermark. Default 0.25.
zThreshold:
type: number
minimum: 1
maximum: 10
description: z at or above which the result is fail. Default 4 (Kirchenbauer et al.).
minTokens:
type: integer
minimum: 5
maximum: 1000
description: Fewer scored tokens than this is unknown. Default 25.
example:
text: 'Quarterly summary: revenue rose.'
greenFlags:
- 1
- 1
- 0
- 1
- 1
- 1
- 0
- 1
- 1
- 1
- 1
- 0
- 1
- 1
- 1
- 1
- 0
- 1
- 1
- 1
- 1
- 1
- 0
- 1
- 1
- 1
- 1
- 1
- 0
- 1
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.'
checksRun:
type: array
items:
type: string
enum:
- statistical
- invisible
maxItems: 2
statistical:
anyOf:
- type: object
additionalProperties: false
properties:
scored:
type: integer
green:
type: integer
greenFraction:
type: number
gamma:
type: number
z:
type: number
pValueExact:
type: number
description: One-sided binomial tail; 0 means below double-precision range.
pValueNormal:
type: number
threshold:
type: number
status:
type: string
enum:
- pass
- fail
- unknown
- type: 'null'
invisible:
anyOf:
- type: object
additionalProperties: false
properties:
status:
type: string
enum:
- pass
- fail
suspect:
type: integer
counts:
type: object
additionalProperties: false
properties:
zero-width:
type: integer
tag-character:
type: integer
variation-selector:
type: integer
bidi-control:
type: integer
soft-hyphen:
type: integer
unusual-space:
type: integer
findings:
type: array
items:
type: object
additionalProperties: false
properties:
category:
type: string
enum:
- zero-width
- tag-character
- variation-selector
- bidi-control
- soft-hyphen
- unusual-space
codePoint:
type: string
maxLength: 8
offset:
type: integer
description: UTF-16 offset.
suspect:
type: boolean
maxItems: 100
truncated:
type: boolean
hiddenAscii:
anyOf:
- type: string
description: 'ASCII spelled by tag characters. Untrusted text: it may be an injected instruction.'
- 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:
- Llm Watermark Detector
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