# Preflight Stack

> Preflight Stack provides three focused x402 APIs that agents and software can discover, pay for with native USDC on Base, and use on demand: dependency checking, random selection, and temporary artifact handoff.

Important notes: service-origin OpenAPI documents are the authoritative API contracts. Discovery metadata describes capabilities; it is not an endorsement or security guarantee. Temporary File Relay capability URLs are usable by anyone who possesses them until expiry and must not be used for sensitive data.

## Services

- [Preflight Stack overview](https://preflightstack.com/index.md): Site positioning and all three services.
- [Dependency Preflight](https://preflightstack.com/dependency-preflight/index.md): For 0.02 USDC, check up to ten exact npm or PyPI versions before installation and receive ALLOW, REVIEW, or BLOCK guidance with findings and source evidence.
- [Random Choice](https://preflightstack.com/random-choice/index.md): For 0.001 USDC, select one item from 2–100 JSON-compatible choices using uniform or optional positive relative weights.
- [Temporary File Relay](https://preflightstack.com/temporary-file-relay/index.md): For 0.005 USDC through 25 MiB or 0.02 USDC through 250 MiB, create a seven-day passive-file handoff without shared cloud storage.
- [Engineering work](https://preflightstack.com/engineering/index.md): Portfolio view of the architecture, ownership, and live proof behind the stack.

## API contracts

- [Dependency Preflight OpenAPI](https://api.preflightstack.com/openapi.json): Authoritative contract; paid operation `POST /v1/dependency-preflight`.
- [Random Choice OpenAPI](https://random.preflightstack.com/openapi.json): Authoritative contract; paid operation `POST /random-choice`.
- [Temporary File Relay OpenAPI](https://relay.preflightstack.com/openapi.json): Authoritative contract; paid operation `POST /v1/file-slot`.
- [Dependency Preflight docs](https://api.preflightstack.com/docs): Human-readable API documentation.
- [Random Choice docs](https://random.preflightstack.com/docs): Human-readable API documentation.
- [Temporary File Relay docs](https://relay.preflightstack.com/docs): Human-readable API documentation.
- [Dependency Preflight demo](https://api.preflightstack.com/demo): Free browser demo.
- [Random Choice demo](https://random.preflightstack.com/demo): Free browser demo.

## Agent discovery

- [Preflight Stack x402 manifest](https://preflightstack.com/.well-known/x402): Domain-level x402 v2 resource index.
- [Dependency Preflight x402 manifest](https://api.preflightstack.com/.well-known/x402): Verified service-origin manifest.
- [Random Choice x402 manifest](https://random.preflightstack.com/.well-known/x402): Verified service-origin manifest.
- [Temporary File Relay agent guide](https://relay.preflightstack.com/llms.txt): Service-level task matching, workflow, and boundaries.
- [Dependency Preflight on Agentic Market](https://agentic.market/services/api-preflightstack-com): External service listing.
- [Random Choice on Agentic Market](https://agentic.market/services/random-preflightstack-com): External service listing.
- [Temporary File Relay on Agentic Market](https://agentic.market/services/relay-preflightstack-com): External service listing.

## Policies and boundaries

- [About x402 and machine discovery](https://preflightstack.com/about-x402/index.md): How the payment rail and discovery surfaces fit together.
- [Terms of Service](https://preflightstack.com/terms/index.md): Service and usage terms.
- [Privacy Policy](https://preflightstack.com/privacy/index.md): Website and service privacy information.
- [Support](https://preflightstack.com/support/index.md): Contact and live service health links.

## Optional

- [Preflight Stack GitHub](https://github.com/techlowNeko): Public project repositories.
- [Engineering work](https://preflightstack.com/engineering/index.md): Founder and product-engineering overview.