{"scheme":"x402","name":"x402","summary":"Stablecoin HTTP 402 created by Coinbase: the server lists acceptable payment options; the client signs a payment for one and retries; a facilitator verifies and settles on-chain.","status":"Open protocol (Apache-2.0); v2 is current and v1 remains in use.","settlement":"On-chain on EVM networks (e.g. Base) and Solana — block-bound, typically seconds.","challenge":{"where":"v2: PAYMENT-REQUIRED header (base64 JSON). v1: JSON response body.","format":"{ x402Version, accepts: [{ scheme, network, amount (v2) | maxAmountRequired (v1), asset, payTo, maxTimeoutSeconds, extra }] }"},"credential":{"where":"v2: PAYMENT-SIGNATURE header. v1: X-PAYMENT header.","format":"Base64-encoded signed payment payload for the chosen requirement, echoed exactly as received."},"receipt":{"where":"v2: PAYMENT-RESPONSE header. v1: X-PAYMENT-RESPONSE header.","format":"Base64-encoded settlement result."},"notes":["Read x402Version before choosing header names — mixing v1 and v2 names fails.","v2 networks are CAIP-2 identifiers, e.g. eip155:8453 for Base.","Amounts are atomic units of the asset — 10000 is 0.01 USDC (6 decimals).","Many facilitators charge no fee; gas is handled on-chain."],"flow":["Client requests the resource.","Server replies 402 with PAYMENT-REQUIRED (v2) listing accepted options.","Client picks an option and signs a payment payload with an x402 client.","Client retries with PAYMENT-SIGNATURE carrying the payload.","Server verifies and settles through a facilitator, serves the resource, and returns PAYMENT-RESPONSE."],"example":"HTTP/1.1 402 Payment Required\nPAYMENT-REQUIRED: eyJ4NDAyVmVyc2lvbiI6Miwi...\n\nGET /resource HTTP/1.1\nPAYMENT-SIGNATURE: eyJ4NDAyVmVyc2lvbiI6Miwi...","specs":[{"title":"x402 documentation","url":"https://docs.x402.org/"},{"title":"x402: HTTP 402","url":"https://docs.x402.org/core-concepts/http-402"},{"title":"x402 FAQ (networks, fees)","url":"https://docs.x402.org/faq"}],"implementations":[{"id":"x402-protocol","name":"x402 Protocol","roles":["pay","charge"],"kind":"protocol","url":"https://402mcp.org/solutions/x402-protocol"},{"id":"cloudflare-agents-x402","name":"Cloudflare Agents SDK (x402)","roles":["pay","charge"],"kind":"sdk","url":"https://402mcp.org/solutions/cloudflare-agents-x402"},{"id":"coinbase-payments-mcp","name":"Coinbase Payments MCP","roles":["pay"],"kind":"mcp-server","url":"https://402mcp.org/solutions/coinbase-payments-mcp"},{"id":"thirdweb-x402","name":"thirdweb x402","roles":["pay","charge"],"kind":"facilitator","url":"https://402mcp.org/solutions/thirdweb-x402"},{"id":"payai-x402-facilitator","name":"PayAI Network","roles":["charge"],"kind":"facilitator","url":"https://402mcp.org/solutions/payai-x402-facilitator"},{"id":"vercel-402-mcp-middleware","name":"x402-mcp (Vercel)","roles":["pay","charge"],"kind":"sdk","url":"https://402mcp.org/solutions/vercel-402-mcp-middleware"},{"id":"crossmint-agent-wallets","name":"Crossmint Agent Wallets","roles":["pay"],"kind":"wallet","url":"https://402mcp.org/solutions/crossmint-agent-wallets"},{"id":"stripe-machine-payments","name":"Stripe Machine Payments","roles":["charge"],"kind":"platform","url":"https://402mcp.org/solutions/stripe-machine-payments"}]}