x402 specification

org: Coinbase + community

category: spec

status: spec

x402Methods: exact stripe method-agnostic

notes: The HTTP-status-402 protocol that revives the long-dormant "Payment Required" status code as a machine-payable handshake. Method-agnostic by design: "exact" for direct on-chain transfers, "stripe" for the Stripe Link variant, future methods can be added.


TensorFeed.ai

org: Pizza Robot Studios

category: publisher

status: live

notes: Real-time AI-ecosystem data with 14 paid premium endpoints. AFTA-certified: code-enforced no-charge guarantees plus Ed25519-signed receipts on every paid call. End-to-end USDC loop verified on Base mainnet 2026-04-27.


TerminalFeed.io

notes: Real-time data dashboard. AFTA-federated with TensorFeed: a single bearer token works on both sites via the cross-Worker validate + commit rail. Independent Ed25519 receipt keypair, shared credit ledger.


Stripe Link Agents

org: Stripe

status: announced

networks: ethereum-mainnet base

notes: April 2026 announcement: Stripe Link extended to AI agents using x402 with a `stripe` method for Shared Payment Tokens. Same x402 protocol envelope, different settlement scheme. General availability rolling out across the Stripe payments platform through 2026.


org: Coinbase

category: sdk

status: sdk

networks: base ethereum-mainnet

notes: Reference TypeScript SDK from Coinbase. Provides client + server middleware for the `exact` x402 method, plus Express/Fastify/Hono adapters. The fastest way to add x402 to an existing Node API.


tensorfeed (Python)

notes: Python SDK with optional [web3] extra for one-call USDC sign-and-send. Targets the TensorFeed API but the payment helpers are reusable for any AFTA-compliant publisher.


tensorfeed (JavaScript)

notes: TypeScript SDK with full coverage of free + premium endpoints and the x402 confirm flow.


afta-gateway

category: gateway

status: gateway

notes: Drop-in Cloudflare Worker template. Wraps any HTTP API in AFTA primitives: USDC verification, bearer-token credits, Ed25519-signed receipts, code-enforced no-charge ledger. MIT, no protocol fee, no signup. Fork, set 3 secrets, deploy.


tensorfeed-mcp (MCP server)

category: reference

notes: MCP server that consumes a TensorFeed bearer token (paid via USDC on Base) and exposes 14 paid tools to any MCP client (Claude Desktop, Claude Code, Cursor, Cline, etc). Reference example of how an MCP server can wrap an x402 publisher.