The Join Cardinality API from WritersLogic Verifiable AI Agent Hub — 1 operation(s) for join cardinality.
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openapi: 3.2.0
info:
title: WritersLogic Verifiable AI Agent Hub Join Cardinality 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: Join Cardinality
paths:
/api/v1/join-cardinality:
post:
operationId: join_cardinality
summary: Row multiplication, unmatched keys and uniqueness violations before a table join
description: 'Takes the join keys of two tables (every row''s key, or distinct keys with row counts) and computes the exact output row count of an inner, left, right or full equi-join with SQL NULL semantics, the observed cardinality (one-to-one, one-to-many, many-to-one, many-to-many), the keys that multiply rows the most, unmatched keys on each side and the first duplicate row when a side was assumed unique. It also flags keys that match only after loose coercion (7 vs "7", "007" vs 7, trailing spaces, case), which silently join nothing in a typed engine. For agents about to merge, enrich or deduplicate tables. It sees only the keys you send: it does not read data, and it cannot know whether a composite key is complete.
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: developer
x-sample-url: https://agents.writerslogic.com/api/v1/samples/join-cardinality
security:
- x402: []
- apiKey: []
requestBody:
required: true
content:
application/json:
schema:
type: object
additionalProperties: false
required:
- left
- right
- joinType
properties:
left:
type: object
additionalProperties: false
properties:
keys:
type: array
maxItems: 20000
items:
description: 'One row''s join key: a string, number or boolean, null for SQL NULL, or an array of those for a composite key.'
description: Join key of every row, in table order.
counts:
type: array
maxItems: 5000
items:
type: object
additionalProperties: false
required:
- key
- count
properties:
key:
description: A join key (scalar, null, or array for composite).
count:
type: integer
minimum: 1
maximum: 1000000
description: 'Key summary: how many rows carry each distinct key.'
nullRows:
type: integer
minimum: 0
maximum: 1000000
description: 'With counts: rows whose key is NULL.'
right:
type: object
additionalProperties: false
properties:
keys:
type: array
maxItems: 20000
items:
description: 'One row''s join key: a string, number or boolean, null for SQL NULL, or an array of those for a composite key.'
description: Join key of every row, in table order.
counts:
type: array
maxItems: 5000
items:
type: object
additionalProperties: false
required:
- key
- count
properties:
key:
description: A join key (scalar, null, or array for composite).
count:
type: integer
minimum: 1
maximum: 1000000
description: 'Key summary: how many rows carry each distinct key.'
nullRows:
type: integer
minimum: 0
maximum: 1000000
description: 'With counts: rows whose key is NULL.'
joinType:
type: string
enum:
- inner
- left
- right
- full
expect:
type: object
additionalProperties: false
properties:
leftUnique:
type: boolean
description: Left keys (non-NULL) must be distinct.
rightUnique:
type: boolean
description: Right keys (non-NULL) must be distinct.
everyLeftMatched:
type: boolean
everyRightMatched:
type: boolean
noRowMultiplication:
type: boolean
description: The output must not have more rows than the preserved side.
maxOutputRows:
type: integer
minimum: 0
maximum: 9000000000000000
normalize:
type: object
additionalProperties: false
properties:
trim:
type: boolean
caseFold:
type: boolean
description: Normalization your pipeline applies to string keys before joining.
example:
left:
keys:
- 1
- 2
- 3
- 3
- null
- '007'
right:
keys:
- 1
- 3
- 3
- 4
- '7'
- ' 1'
joinType: left
expect:
rightUnique: true
noRowMultiplication: true
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.'
left:
type: object
properties:
rows:
type: integer
distinctKeys:
type: integer
nullKeyRows:
type: integer
maxMultiplicity:
type: integer
unique:
type: boolean
right:
type: object
properties:
rows:
type: integer
distinctKeys:
type: integer
nullKeyRows:
type: integer
maxMultiplicity:
type: integer
unique:
type: boolean
observedCardinality:
type: string
enum:
- one-to-one
- one-to-many
- many-to-one
- many-to-many
outputRows:
type: object
properties:
inner:
type: integer
left:
type: integer
right:
type: integer
full:
type: integer
selected:
type: integer
multiplicationFactor:
anyOf:
- type: number
description: Selected join's output rows divided by the preserved side's rows (left for inner/left/full, right for right).
- type: 'null'
unmatched:
type: object
properties:
leftKeys:
type: integer
rightKeys:
type: integer
leftRows:
type: integer
rightRows:
type: integer
leftSample:
type: array
items:
description: Key
rightSample:
type: array
items:
description: Key
fanOut:
type: array
items:
type: object
properties:
key:
description: Join key
leftRows:
type: integer
rightRows:
type: integer
outputRows:
type: integer
coercionHazards:
type: array
items:
type: object
properties:
kind:
type: string
left:
description: Left key
right:
description: Right key
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:
- Join Cardinality
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