# x402.fb

> The Fractal Bitcoin rail for HTTP 402 agent payments. Priced in FB sats (≈$ display). Non-custodial. Locally verified.

## Product
- Marketplace: discover paid Fractal capabilities, pay per call in FB
- Provider console: register xpub, get API key, charge FB per request
- Playground: UniSat PSBT → rawTx settle → receipt
- Agent kit: MCP (x402_search / get / call / BIP-322 sign·verify·derive), Claude skill, OpenClaw wrapper
- Local BIP-322 + FB derive: agent-kit/signer (keys stay local). DLC/PSBT: NexumBit Python Signer

## Protocol
- Scheme: `fb-exact` on `fractal-mainnet`
- Settlement: one 2-output FB tx (provider xpub address + facilitator fee)
- Prefer `X-PAYMENT-RAWTX` for local out verification
- Open protocol / SDK: https://github.com/The-Lonely-Bit/os-x402.fb (MIT)
- Hosted marketplace is a commercial discovery layer on top of the rail
- BIP-322: sign locally; hosted verify-only at POST /v1/verify-bip322 (no private keys accepted)

## Key URLs (absolute — for agent indexes)
- Marketplace: https://x402.fractal.thelonelybit.org
- API / facilitator: https://x402.fractal.api.thelonelybit.org
- Well-known (x402scan): https://x402.fractal.api.thelonelybit.org/.well-known/x402
- Well-known JSON: https://x402.fractal.api.thelonelybit.org/.well-known/x402.json
- Directory submit payload: https://x402.fractal.api.thelonelybit.org/.well-known/x402/submit
- tools.json: https://x402.fractal.api.thelonelybit.org/v1/tools.json
- tools.json (root alias): https://x402.fractal.api.thelonelybit.org/tools.json
- discover: https://x402.fractal.api.thelonelybit.org/v1/discover
- scheme: https://x402.fractal.api.thelonelybit.org/v1/scheme/fb-exact
- price (FB/USDT ≈ USD): https://x402.fractal.api.thelonelybit.org/v1/price/fb
- BIP-322 verify: https://x402.fractal.api.thelonelybit.org/v1/verify-bip322
- Settlement receipts: https://x402.fractal.api.thelonelybit.org/v1/receipts/:txid
- MCP install: https://x402.fractal.api.thelonelybit.org/mcp.json
- NexumBit Signer (DLC/PSBT): https://github.com/The-Lonely-Bit/Taproot-based_Discreet_Log_Contracts/tree/main/Signer

## Agents
- Add to Claude / Cursor: paste mcpServers from /mcp.json (keys stay local)
- Listing pages: one-click agent snippet + MCP prompt
- Playground → shareable receipt URL on marketplace `/receipt/:txid`

## Trust model
Non-custodial (no private keys held). Settlement is locally verified from rawTx when provided — not full consensus trustlessness. USD figures are FB/USDT spot estimates only. Never send WIF to the API.