Facilitator - Compose.Market

The facilitator endpoints expose the x402 pieces directly. The payment intent endpoints expose the Compose reserve-settle-abort flow used by Compose Keys and metered calls.

x402 endpoints

Method	Path	Purpose
`GET`	`/api/x402/facilitator/supported`	Lists supported x402 versions, networks, and schemes.
`GET`	`/api/x402/facilitator/chains`	Lists configured chains, CAIP-2 network IDs, USDC addresses, explorers, and default chain ID.
`POST`	`/api/x402/facilitator/verify`	Verifies a payment payload against payment requirements.
`POST`	`/api/x402/facilitator/settle`	Settles a payment payload.

verify and settle accept x402-shaped paymentPayload and paymentRequirements objects.

Payment-required challenge

Raw x402 calls start with a normal request. If no valid payment is present, Compose responds with:

HTTP/1.1 402 Payment Required
PAYMENT-REQUIRED: <base64-json>
Content-Type: application/json

The client signs the requirement and retries with:

PAYMENT-SIGNATURE: <signed-payment-payload>

Payment intents

Method	Path	Purpose
`POST`	`/api/payments/prepare`	Authorizes an exact amount, a metered quote, or a budget cap.
`POST`	`/api/payments/settle`	Settles an intent with a final amount or metered usage.
`POST`	`/api/payments/abort`	Releases a prepared intent when work fails before settlement.
`POST`	`/api/payments/meter/model`	Prices model usage using catalog pricing.

Quote model usage

POST /api/payments/meter/model
Content-Type: application/json

{
  "modelId": "gpt-5.5",
  "provider": "azure",
  "modality": "text",
  "usage": {
    "promptTokens": 1000,
    "completionTokens": 250,
    "totalTokens": 1250
  }
}

The response contains the resolved model, meter subject, line items, provider amount, platform fee, and final USDC atomic amount.

Receipt headers

Header	Meaning
`PAYMENT-RESPONSE`	Encoded x402 settlement response.
`X-Transaction-Hash`	Settlement transaction hash when available.
`X-Receipt`	Compose receipt with amount, network, line items, and settlement time.
`x-payment-intent-id`	Prepared payment intent ID.

​x402 endpoints

​Payment-required challenge

​Payment intents

​Quote model usage

​Receipt headers

​Related

x402 endpoints

Payment-required challenge

Payment intents

Quote model usage

Receipt headers

Related