> ## Documentation Index > Fetch the complete documentation index at: https://docs.useselo.xyz/llms.txt > Use this file to discover all available pages before exploring further. # Run a preflight > Check, for free, that a target can be tested before you pay. Selo checks the authorization, sends one unpaid request to the target (with `requestBody` for `POST`, 10 second timeout, redirects not followed), reads its x402 v2 challenge, and requires an `exact` USDC payment on Algorand priced at or below the per-job spend limit (0.50 USDC). It also looks the target up in the Bazaar catalog and stores what it finds with the preflight. An eligible preflight is valid for 15 minutes. ## OpenAPI ````yaml /openapi.json post /v1/preflight openapi: 3.1.0 info: title: Selo API version: 1.0.0 summary: CI for x402. It pays your endpoint before your users do. description: >- Selo is a release gate for paid x402 APIs on Algorand. You authorize your endpoint, run a free preflight, then pay Selo 1.00 USDC over x402. Only after that payment settles does Selo pay your endpoint as a real x402 client, run five release checks and return a deterministic PASS, FAIL or INCONCLUSIVE verdict with an Ed25519-signed attestation. There are no API keys. Access to a target is granted per target by authorization; the only paid route is `POST /v1/release-test`, paid with x402. Bodies are JSON, at most 64 KiB. contact: name: Selo url: https://useselo.xyz servers: - url: https://api.useselo.xyz description: Production, Algorand Mainnet security: [] tags: - name: Authorizations description: Prove you control the target before Selo sends it anything. - name: Preflight description: Check for free that a target can be tested and is within budget. - name: Release tests description: The paid x402 route that runs the release checks. - name: Reports description: Private, token-addressed reports of finished release tests. - name: Attestation keys description: Public keys that verify signed verdicts. - name: Discovery description: Machine-readable descriptions of Selo. - name: Health description: Liveness. paths: /v1/preflight: post: tags: - Preflight summary: Run a preflight description: >- Check, for free, that a target can be tested before you pay. Selo checks the authorization, sends one unpaid request to the target (with `requestBody` for `POST`, 10 second timeout, redirects not followed), reads its x402 v2 challenge, and requires an `exact` USDC payment on Algorand priced at or below the per-job spend limit (0.50 USDC). It also looks the target up in the Bazaar catalog and stores what it finds with the preflight. An eligible preflight is valid for 15 minutes. operationId: createPreflight requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/PreflightRequest' examples: post: summary: POST route with a body value: authorizationId: auth_… targetUrl: https://api.example.com/v1/orders method: POST requestBody: sku: demo-widget quantity: 1 get: summary: GET route value: authorizationId: auth_… targetUrl: https://api.example.com/v1/quote method: GET responses: '201': description: The target is eligible. content: application/json: schema: $ref: '#/components/schemas/PreflightEligible' examples: eligible: summary: Eligible value: eligible: true preflightId: pfl_… target: url: https://api.example.com/v1/orders method: POST priceUsdc: '0.01' estimatedMaxSpendUsdc: '0.01' seloPriceUsdc: '1.00' expiresAt: '2026-10-26T12:15:00.000Z' '400': description: >- The body fails validation (`ApiError`), or the target URL is invalid or not https (`PreflightIneligible`, `preflightId` is `null`). content: application/json: schema: anyOf: - $ref: '#/components/schemas/PreflightIneligible' - $ref: '#/components/schemas/ApiError' examples: TARGET_URL_INVALID: summary: TARGET_URL_INVALID value: eligible: false preflightId: null reason: TARGET_URL_INVALID message: The target URL is not a valid absolute URL TARGET_NOT_HTTPS: summary: TARGET_NOT_HTTPS value: eligible: false preflightId: null reason: TARGET_NOT_HTTPS message: Only https targets can be tested VALIDATION_FAILED: summary: Body on a GET value: error: VALIDATION_FAILED message: |- ✖ requestBody is only allowed with POST → at requestBody '403': description: >- No verified, unexpired authorization covers this origin, path and method. `preflightId` is `null` when the authorization ID is unknown. content: application/json: schema: $ref: '#/components/schemas/PreflightIneligible' examples: AUTHORIZATION_MISSING: summary: AUTHORIZATION_MISSING value: eligible: false preflightId: pfl_… reason: AUTHORIZATION_MISSING message: >- No verified authorization covers this target origin, route and method AUTHORIZATION_EXPIRED: summary: AUTHORIZATION_EXPIRED value: eligible: false preflightId: pfl_… reason: AUTHORIZATION_EXPIRED message: >- The authorization is not verified or has expired; verify it again '413': $ref: '#/components/responses/PayloadTooLarge' '422': description: >- The target cannot be tested. Probe rejections carry a stored `preflightId`; a blocked hostname found while parsing the URL has `preflightId: null`. content: application/json: schema: $ref: '#/components/schemas/PreflightIneligible' examples: TARGET_ADDRESS_BLOCKED: summary: TARGET_ADDRESS_BLOCKED value: eligible: false preflightId: pfl_… reason: TARGET_ADDRESS_BLOCKED message: >- The target must be a public hostname on the default https port TARGET_UNREACHABLE: summary: TARGET_UNREACHABLE value: eligible: false preflightId: pfl_… reason: TARGET_UNREACHABLE message: >- The target could not be reached or answered with a server error NO_PAYMENT_CHALLENGE: summary: NO_PAYMENT_CHALLENGE value: eligible: false preflightId: pfl_… reason: NO_PAYMENT_CHALLENGE message: >- The target did not answer the unpaid request with a valid x402 challenge NETWORK_NOT_SUPPORTED: summary: NETWORK_NOT_SUPPORTED value: eligible: false preflightId: pfl_… reason: NETWORK_NOT_SUPPORTED message: >- The target offers no exact payment on the Algorand network Selo pays on ASSET_NOT_SUPPORTED: summary: ASSET_NOT_SUPPORTED value: eligible: false preflightId: pfl_… reason: ASSET_NOT_SUPPORTED message: >- The target offers no exact payment in USDC on the Algorand network PRICE_OVER_BUDGET: summary: PRICE_OVER_BUDGET value: eligible: false preflightId: pfl_… reason: PRICE_OVER_BUDGET message: >- The target price exceeds the per-job downstream spend limit '500': $ref: '#/components/responses/InternalError' components: schemas: PreflightRequest: type: object additionalProperties: false required: - authorizationId - targetUrl - method properties: authorizationId: type: string maxLength: 64 description: A verified authorization that covers this origin, path and method. targetUrl: type: string maxLength: 2048 format: uri description: >- Absolute `https` URL of the paid route. A query string is sent to the target; coverage is checked on origin and path. method: $ref: '#/components/schemas/HttpMethod' requestBody: description: >- JSON body Selo sends to the target on every request of this test. Only with `POST`. Any JSON value except `null`, at most 16 KiB (16384 bytes) once serialized. Omit it to send no body. type: - object - array - string - number - boolean PreflightEligible: type: object description: >- The target can be tested. Pass `preflightId` to `POST /v1/release-test` before `expiresAt`. required: - eligible - preflightId - target - estimatedMaxSpendUsdc - seloPriceUsdc - expiresAt properties: eligible: type: boolean const: true preflightId: type: string description: '`pfl_` plus 26 Crockford base32 characters.' target: type: object required: - url - method - priceUsdc properties: url: type: string description: Normalized target URL (fragment removed). method: $ref: '#/components/schemas/HttpMethod' priceUsdc: type: string pattern: ^[0-9]+\.[0-9]{2,6}$ description: Price the target asked for in its 402 challenge. estimatedMaxSpendUsdc: type: string pattern: ^[0-9]+\.[0-9]{2,6}$ description: >- What Selo expects to pay the target: one paid request at the target's price. seloPriceUsdc: type: string pattern: ^[0-9]+\.[0-9]{2,6}$ description: What the release test costs you, paid to Selo over x402. expiresAt: type: string format: date-time description: The preflight is valid for 15 minutes. PreflightIneligible: type: object description: The target cannot be tested. Nothing was paid. required: - eligible - preflightId - reason - message properties: eligible: type: boolean const: false preflightId: type: - string - 'null' description: >- ID of the stored preflight, or `null` when Selo refused the request before storing it (invalid URL, blocked hostname, unknown authorization). reason: $ref: '#/components/schemas/PreflightRejection' message: type: string ApiError: type: object description: Error body returned by every failing request. required: - error - message properties: error: type: string description: Stable machine-readable error code, for example `VALIDATION_FAILED`. message: type: string description: Human-readable explanation. Do not parse it. HttpMethod: type: string enum: - GET - POST description: HTTP method Selo uses to call the target. PreflightRejection: type: string enum: - AUTHORIZATION_MISSING - AUTHORIZATION_EXPIRED - TARGET_URL_INVALID - TARGET_NOT_HTTPS - TARGET_ADDRESS_BLOCKED - METHOD_NOT_ALLOWED - TARGET_UNREACHABLE - NO_PAYMENT_CHALLENGE - NETWORK_NOT_SUPPORTED - ASSET_NOT_SUPPORTED - PRICE_OVER_BUDGET description: Why a target is not eligible for a release test. responses: PayloadTooLarge: description: The request body is larger than 64 KiB (65536 bytes). content: application/json: schema: $ref: '#/components/schemas/ApiError' examples: PAYLOAD_TOO_LARGE: summary: Body over 64 KiB value: error: PAYLOAD_TOO_LARGE message: Request body exceeds 65536 bytes InternalError: description: Unexpected server error. content: application/json: schema: $ref: '#/components/schemas/ApiError' examples: INTERNAL: summary: Unexpected server error value: error: INTERNAL message: Internal server error ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.