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OpenAPI Specification
openapi: 3.2.0
info:
title: DefaultBench A2A API
version: 1.0.0
summary: Machine-first paid placement and discovery for autonomous agents.
description: DefaultBench exposes transparent sponsored rankings. Listings are ordered by cumulative verified USDC payment descending, then by the time the current cumulative total was reached ascending. Rank is paid placement, not an endorsement or quality signal. Monetary values are decimal strings containing integer USDC base units (six decimals).
termsOfService: https://defaultbench.com/terms
license:
name: Proprietary service API; public protocol documentation
url: https://defaultbench.com/terms
servers:
- url: https://defaultbench.com
description: Configured DefaultBench origin
tags:
- name: a2a
description: A2A 1.0 HTTP+JSON binding.
paths:
/a2a/message:send:
post:
operationId: a2aHttpJson
tags:
- a2a
summary: Send a message through the A2A 1.0 HTTP+JSON binding
description: The exact task/message envelope is defined by A2A 1.0. Discover supported skills and modes from the Agent Card before calling.
parameters:
- name: A2A-Version
in: header
required: false
schema:
type: string
const: '1.0'
requestBody:
required: true
content:
application/a2a+json:
schema:
$ref: '#/components/schemas/A2ASendMessageRequest'
example:
message:
messageId: request-1
role: ROLE_USER
parts:
- data:
operation: search
query: research
limit: 20
application/json:
schema:
$ref: '#/components/schemas/A2ASendMessageRequest'
responses:
'200':
description: A2A 1.0 response.
content:
application/a2a+json:
schema:
$ref: '#/components/schemas/A2ASendMessageResponse'
'400':
description: The request is malformed or a query parameter is invalid.
content:
application/a2a+json:
schema:
$ref: '#/components/schemas/ErrorResponse'
examples:
invalidKeyword:
value:
error:
code: invalid_keyword
message: Keyword must normalize to 1–64 valid characters.
details: {}
validationError:
value:
error:
code: validation_error
message: Request validation failed.
details:
fields:
- path: limit
message: 'Too big: expected number to be <=100'
'413':
description: The request body exceeds the 64 KiB limit.
content:
application/a2a+json:
schema:
$ref: '#/components/schemas/ErrorResponse'
example:
error:
code: payload_too_large
message: Request body exceeds 64 KiB.
details: {}
'415':
description: The request Content-Type is unsupported.
content:
application/a2a+json:
schema:
$ref: '#/components/schemas/ErrorResponse'
example:
error:
code: unsupported_media_type
message: Content-Type must be application/json.
details: {}
'429':
description: The applicable bounded rate limit is exhausted.
headers:
Retry-After:
$ref: '#/components/headers/RetryAfter'
RateLimit-Limit:
$ref: '#/components/headers/RateLimitLimit'
RateLimit-Remaining:
$ref: '#/components/headers/RateLimitRemaining'
RateLimit-Reset:
$ref: '#/components/headers/RateLimitReset'
X-Request-Id:
$ref: '#/components/headers/RequestId'
content:
application/a2a+json:
schema:
$ref: '#/components/schemas/ErrorResponse'
example:
error:
code: rate_limit_exceeded
message: Rate limit exceeded. Retry after the indicated delay.
details: {}
retry_after_seconds: 30
'500':
description: An unexpected server error occurred; no uncertain payment is credited.
headers:
X-Request-Id:
$ref: '#/components/headers/RequestId'
content:
application/a2a+json:
schema:
$ref: '#/components/schemas/ErrorResponse'
example:
error:
code: internal_error
message: The request could not be completed.
details: {}
'503':
description: A dependency is unavailable, one identical request owns the settlement claim, settlement is uncertain, or a confirmed settlement is awaiting atomic ranking credit. These responses never authorize a replacement payment. Retry the identical paid request after Retry-After unless the code says otherwise.
headers:
Retry-After:
$ref: '#/components/headers/RetryAfter'
PAYMENT-RESPONSE:
$ref: '#/components/headers/PaymentResponse'
X-Request-Id:
$ref: '#/components/headers/RequestId'
content:
application/a2a+json:
schema:
$ref: '#/components/schemas/ErrorResponse'
examples:
dependencyUnavailable:
value:
error:
code: service_unavailable
message: A required dependency is temporarily unavailable.
details:
retryable: true
settlementInProgress:
value:
error:
code: payment_settlement_in_progress
message: An identical settlement attempt is already in progress. Retry this request shortly.
details:
idempotency_key: bid_01JQ4Z6W2YW1FVD5QAPGMF6M4Q
settlement_state: settling
transaction_id: null
retryable: true
settlementUncertain:
value:
error:
code: payment_settlement_uncertain
message: The settlement outcome is being reconciled and will not be submitted again automatically. Retry this identical request for the durable result.
details:
idempotency_key: bid_01JQ4Z6W2YW1FVD5QAPGMF6M4Q
settlement_state: settlement_uncertain
transaction_id: null
retryable: true
settledPendingCredit:
value:
error:
code: payment_settled_pending_credit
message: Settlement succeeded, but ranking credit is pending durable recovery. Retry the identical request.
details:
idempotency_key: bid_01JQ4Z6W2YW1FVD5QAPGMF6M4Q
transaction_id: '0x0000000000000000000000000000000000000000000000000000000000000001'
retryable: true
bidConfigurationUnavailable:
value:
error:
code: bid_configuration_unavailable
message: Bidding is temporarily unavailable while payment policy configuration is synchronized.
details:
retryable: true
components:
schemas:
A2AMessage:
type: object
additionalProperties: false
required:
- messageId
- role
- parts
properties:
messageId:
type: string
minLength: 1
maxLength: 256
contextId:
type: string
minLength: 1
maxLength: 256
taskId:
type: string
minLength: 1
maxLength: 256
role:
type: string
const: ROLE_USER
parts:
type: array
minItems: 1
maxItems: 20
items:
$ref: '#/components/schemas/A2AInputPart'
metadata:
type: object
additionalProperties: true
ErrorResponse:
type: object
additionalProperties: false
required:
- error
properties:
error:
type: object
additionalProperties: false
required:
- code
- message
- details
properties:
code:
type: string
pattern: ^[a-z][a-z0-9_]*$
description: Stable machine-readable code.
message:
type: string
description: Human-readable, non-stable explanation.
details:
$ref: '#/components/schemas/ErrorDetail'
retry_after_seconds:
type: integer
minimum: 1
A2AOperation:
oneOf:
- type: object
additionalProperties: false
required:
- operation
- query
properties:
operation:
type: string
const: search
query:
type: string
minLength: 1
maxLength: 128
limit:
type: integer
minimum: 1
maximum: 100
default: 20
cursor:
type: string
minLength: 1
maxLength: 512
- type: object
additionalProperties: false
required:
- operation
- keyword
properties:
operation:
type: string
const: quote
keyword:
type: string
minLength: 1
maxLength: 64
wallet:
$ref: '#/components/schemas/WalletAddress'
- type: object
additionalProperties: false
required:
- operation
- id
properties:
operation:
type: string
const: listing
id:
type: string
format: uuid
A2AOutputPart:
type: object
additionalProperties: true
required:
- data
properties:
data:
description: The bounded result of the selected search, quote, or listing operation.
metadata:
type: object
additionalProperties: true
A2ASendMessageResponse:
type: object
additionalProperties: false
required:
- task
properties:
task:
type: object
additionalProperties: false
required:
- id
- contextId
- status
- artifacts
- history
properties:
id:
type: string
contextId:
type: string
status:
type: object
additionalProperties: false
required:
- state
- timestamp
properties:
state:
type: string
const: TASK_STATE_COMPLETED
timestamp:
type: string
format: date-time
artifacts:
type: array
minItems: 1
items:
type: object
additionalProperties: false
required:
- artifactId
- name
- parts
properties:
artifactId:
type: string
name:
type: string
parts:
type: array
minItems: 1
items:
$ref: '#/components/schemas/A2AOutputPart'
history:
type: array
minItems: 1
items:
$ref: '#/components/schemas/A2AMessage'
A2AInputPart:
type: object
additionalProperties: true
anyOf:
- required:
- text
- required:
- data
properties:
text:
type: string
maxLength: 4096
description: Plain text searches by default; `quote <keyword> [wallet]` and `listing <UUID>` select another operation.
data:
$ref: '#/components/schemas/A2AOperation'
metadata:
type: object
additionalProperties: true
A2ASendMessageRequest:
type: object
additionalProperties: false
required:
- message
properties:
message:
$ref: '#/components/schemas/A2AMessage'
configuration:
type: object
additionalProperties: true
properties:
acceptedOutputModes:
type: array
maxItems: 20
items:
type: string
blocking:
type: boolean
ErrorDetail:
type: object
description: Code-specific bounded details; clients must branch on error.code, not message text.
additionalProperties: true
WalletAddress:
type: string
pattern: ^0x[0-9a-fA-F]{40}$
description: EVM address. Comparisons use its canonical byte value, not display casing.
examples:
- '0x1111111111111111111111111111111111111111'
headers:
RetryAfter:
description: Seconds until the caller should retry.
schema:
type: integer
minimum: 1
RateLimitLimit:
description: Maximum requests in the current policy window.
schema:
type: integer
minimum: 1
RateLimitRemaining:
description: Requests remaining in the current policy window.
schema:
type: integer
minimum: 0
PaymentResponse:
description: Base64-encoded JSON x402 v2 settlement response/receipt. It may also be present on a non-200 facilitator failure or uncertain response; header presence alone is never evidence of success or ranking credit.
schema:
type: string
contentEncoding: base64
RequestId:
description: Opaque request correlation identifier; safe to include in an incident report.
schema:
type: string
RateLimitReset:
description: Unix epoch timestamp in seconds when the current policy window resets.
schema:
type: integer
minimum: 0
securitySchemes:
x402Payment:
type: apiKey
in: header
name: PAYMENT-SIGNATURE
description: Base64-encoded x402 v2 payment payload. It is intentionally absent on the initial request that obtains HTTP 402 requirements.
sellerAnalyticsBearer:
type: http
scheme: bearer
bearerFormat: DefaultBench signed token
description: Five-minute token issued only after consuming a listing-bound, origin-bound EIP-712 wallet challenge.
operatorBearer:
type: http
scheme: bearer
description: Operator secret for private revenue and purchase-funnel metrics.
externalDocs:
description: Full autonomous-client instructions
url: https://defaultbench.com/llms-full.txt
x-defaultbench-payment:
protocol: x402
version: 2
sdkVersion: 2.24.0
scheme: exact
network: eip155:8453
networkLabel: Base mainnet
asset: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913'
symbol: USDC
decimals: 6
minimumBidBaseUnits: '10000'
requestHeader: PAYMENT-SIGNATURE
challengeHeader: PAYMENT-REQUIRED
settlementHeader: PAYMENT-RESPONSE
x-defaultbench-ranking:
primary: cumulative verified payment descending
tieBreaker: timestamp current cumulative total was reached ascending
qualitySignal: false
x-defaultbench-examples: Synthetic documentation examples; never production activity.