Resources.

Curated links for anyone new to the x402 and agent-commerce stack. We keep this list current and honest. Only what we've actually used.

Protocol

The spec.

x402.org. Specification, reference implementations, ecosystem list.
github.com/coinbase/x402. Reference server and client code.
RFC 7231 § 6.5.2. The original HTTP 402 status, reserved since 1997.
EIP-3009. The "transfer with authorization" standard that makes gasless stablecoin payments possible.

Chain & asset

Base and USDC.

base.org. Coinbase's L2, where agent commerce actually happens.
USDC on Base. Native, not bridged. The default x402 settlement asset.
basescan.org. Block explorer. Verify any settlement tx here.

SDKs

Building paying agents.

Coinbase Developer Platform (CDP). Managed wallets plus x402 facilitator. The easiest path to production.
@x402/axios. Node SDK wrapping axios.
@x402/fetch. Node SDK wrapping native fetch.
x402 (Python). httpx and requests support.
viem. Lightweight Ethereum TypeScript library. What we use for key handling.

Agent frameworks

Discovery and tools.

Model Context Protocol (MCP). How Claude and others import external tools.
A2A (agent-to-agent) protocol. Structured inter-agent communication.
Claude Agent Skills. Packaged capabilities your Claude agent can load.
llms.txt. The machine-readable site index convention.

Ecosystem

Other x402 providers.

ApiToll is part of an ecosystem, not a silo. Some providers and directories worth knowing:

x402scan.com. Directory of x402 endpoints across the ecosystem.
x402 Bazaar. Discoverability layer run by Coinbase.
More to come. We will add reciprocal links as the ecosystem settles.

If you're running an x402 service and want a link here, email us. We link anything we can reach and verify with a real paid call.

Data

Sources we redistribute.

iannuttall/binlist-data. The BIN dataset behind our BIN Lookup product. CC-BY-4.0. Thank you.

Our endpoints

Machine-readable surfaces.

/llms.txt. If you are an LLM, read this first.
/.well-known/mcp.json. MCP server manifest.
/.well-known/agent.json. A2A agent card.
/health. Live status and revenue counter.