How it works
- Discover. Free GET /preview is cached catalog, not_probed.
- Compare. Catalog said X. We observed Y. Separate fields.
- Probe. Probe live is the penny POST /route. Unpaid HTTP 402 at $0.01. A paid hit returns a live URL plus the target contract. A miss returns a typed
miss_reason. - Recommend. Best capability match in the current index.
402Signal recommends the route. Your agent keeps the wallet.
Pulse
Index pending. No market-quality rates until probe history fills. GET /pulse
Developer access
POST /route · GET /preview · POST /validate · GET /attestation · /mcp · /openapi.json · /llms.txt · /rails
Feedback: @402Signal and 402signal@gmail.com. Source: https://github.com/402signal/402signal.
Shared
POST https://402signal.com/route with {"need":"weather"}. Optional url. Optional prefer_network base, solana, or algorand. Unpaid HTTP 402. Sign the matching accepts[] entry. Retry the same POST with PAYMENT-SIGNATURE. HTTP 200 is a live URL plus target {method,inputSchema,facilitator}. HTTP 503 is a typed miss_reason. Amount 10000 atomic USDC = $0.01.
curl -sS -D - https://402signal.com/route -H 'Content-Type: application/json' -d '{"need":"weather"}'
{"need":"weather","url":"https://optional.example","prefer_network":"base"}
curl -sS https://402signal.com/route -H 'Content-Type: application/json' -H "PAYMENT-SIGNATURE: $SIG" -d '{"need":"weather"}'
Front of a larger process
Free GET /preview?need=weather is cached, not_probed, and does not probe. Then paid POST /route for a live probe. Then call the returned URL with target.method and inputSchema. MCP: POST https://402signal.com/mcp tools/call preview (free) then route (paid). Docs /llms.txt OpenAPI /.well-known/x402.json.
curl -sS 'https://402signal.com/preview?need=weather'
{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"preview","arguments":{"need":"weather"}}}
Base
prefer_network base. EVM PAYMENT-SIGNATURE. Hidden Pay $0.01 on Base if an injected wallet exists (MetaMask, Coinbase Wallet, Base App). Chain 8453.
Solana
prefer_network solana. Agent/CLI only. Sign the Solana accept from the 402. x402scan lists Solana/Base; it skips Algorand.
Algorand
prefer_network algorand. Agent/CLI only (no Pera button). USDC ASA 31566704. GoPlausible facilitator. POST /route still returns a live Algo 402 when that's what is up.
Facilitator
The facilitator is echoed from the target accepts. Never default x402.org.