> ## Documentation Index > Fetch the complete documentation index at: https://docs.httpayer.com/llms.txt > Use this file to discover all available pages before exploring further. # Execute x402 payment-gated API call > HTTPayer proxy service for x402 payment-gated API calls. **Flow:** 1. Proxy detects 402 Payment Required from target API 2. HTTPayer wallet executes payment to target API 3. Proxy retries request with payment proof 4. Returns target API response to client **Error Handling:** - 502 Bad Gateway: Target API errors (unreachable, malformed, 5xx) - 500 Internal Server Error: Proxy configuration errors - 4xx Pass-through: Client errors from target API - Timeout detection with configurable limits ## OpenAPI ````yaml post /proxy openapi: 3.0.0 info: title: HTTPayer Proxy API version: 1.0.0 description: >- HTTPayer is a payment router for 402 response codes and the x402 Protocol. Users can access APIs that use the x402 standard through the HTTPayer proxy. contact: name: HTTPayer Team url: https://httpayer.com servers: - url: https://api.httpayer.com description: Production server security: [] tags: - name: Relay description: Cross-chain payment relay endpoints - name: Account description: Account balance and limits endpoints - name: Webhooks description: Async task status and webhooks - name: LLM description: OpenAI-powered endpoints for translation and chat - name: Health description: Health check endpoints paths: /proxy: post: tags: - Proxy summary: Execute x402 payment-gated API call description: | HTTPayer proxy service for x402 payment-gated API calls. **Flow:** 1. Proxy detects 402 Payment Required from target API 2. HTTPayer wallet executes payment to target API 3. Proxy retries request with payment proof 4. Returns target API response to client **Error Handling:** - 502 Bad Gateway: Target API errors (unreachable, malformed, 5xx) - 500 Internal Server Error: Proxy configuration errors - 4xx Pass-through: Client errors from target API - Timeout detection with configurable limits parameters: - in: header name: X-TIMEOUT schema: type: number description: Client timeout in milliseconds (max 120000ms / 2 minutes) required: false requestBody: required: true content: application/json: schema: type: object required: - api_url - method properties: api_url: type: string description: Target API URL to call via proxy example: https://www.x402.org/protected method: type: string enum: - GET - POST - PUT - DELETE - PATCH description: HTTP method for target API example: GET json: type: object description: > JSON body — serialized and sent with Content-Type: application/json. Mirrors Python requests(json=...) / fetch(body: JSON.stringify(...)). example: city: San Francisco data: description: > Form-encoded body when an object, raw string body when a string. Mirrors Python requests(data=...). Object → Content-Type: application/x-www-form-urlencoded. String → passed through as-is; set Content-Type via headers. oneOf: - type: object - type: string body: type: string description: > Pre-serialized body string — passed through unchanged, without setting Content-Type. If you pass an object it will be JSON-stringified, but you must manually set Content-Type: application/json via headers. Use json instead for automatic Content-Type handling. payload: type: object description: Deprecated alias for json. Use json instead. params: type: object description: Query parameters appended to the target URL example: limit: '10' offset: '0' headers: type: object description: Custom headers forwarded to the target API example: Accept: application/json auth: type: object description: > Basic auth shorthand — converted to Authorization: Basic . Mirrors Python requests(auth=("user", "pass")). properties: username: type: string password: type: string cookies: type: object description: | Cookie shorthand — merged into the Cookie header. Mirrors Python requests(cookies={...}). example: session: abc123 timeout: type: number description: >- Per-request timeout in seconds (server default applies if omitted; also accepts X-TIMEOUT header in ms) example: 30 responses: '200': description: Target API request successful content: application/json: schema: type: object description: Response from target API (pass-through) '400': description: Bad request - Invalid parameters content: application/json: schema: $ref: '#/components/schemas/Error' '402': description: Payment Required - Insufficient credits or spend limit exceeded content: application/json: schema: type: object properties: error: type: string example: Insufficient credits '429': description: Too Many Requests - Server at capacity headers: Retry-After: description: Seconds to wait before retrying schema: type: integer example: 5 content: application/json: schema: type: object properties: error: type: string example: Too Many Requests message: type: string example: >- Server is currently processing the maximum number of concurrent requests. Please try again in a moment. details: type: string example: 'Active requests: 100/100' retryAfter: type: integer example: 5 '500': description: Internal Server Error - Proxy configuration error content: application/json: schema: type: object properties: error: type: string example: Internal Server Error message: type: string example: The proxy server encountered an internal error details: type: string '502': description: > Bad Gateway - Target API error, unreachable, or refused payment after retries. When the target API returns 402 after all sync retries, HTTPayer returns 502 with `message: "Upstream API refused payment after N attempts"`. If blockchain polling is active, a `webhook_id` field is included — use `GET /webhooks/:id` to track whether the payment eventually confirmed on-chain. If confirmed, credits are charged; if not, reserved credits are automatically refunded. content: application/json: schema: type: object properties: error: type: string example: Bad Gateway message: type: string example: Upstream API refused payment after 3 attempts details: type: string upstreamStatus: type: number description: HTTP status code from target API (if available) webhook_id: type: string description: >- Webhook ID for tracking async payment detection (present when polling is active) example: 550e8400-e29b-41d4-a716-446655440000 security: - ApiKeyAuth: [] components: schemas: Error: type: object properties: error: type: string description: Error message details: type: string description: Additional error details securitySchemes: ApiKeyAuth: type: apiKey in: header name: x-api-key description: API key for authentication ````