How do I get my API discovered by AI agents?
Agents do not browse websites. They search indexes, so discovery means being in the indexes agents query and describing the endpoint in the words they search for.
1. Coinbase Bazaar
Coinbase's Bazaar is the catalog of x402 endpoints discovered by the CDP facilitator. It is exposed through CDP APIs, the Bazaar MCP server and Amazon Bedrock AgentCore, and browsable by people on agentic.market. There is no registration form: a route built with the CDP SDK carries a Bazaar declaration, and the first paid call settled through the facilitator triggers indexing.
Coinbase's POST /v2/x402/validate endpoint reports, for a given URL, whether it is reachable, returns a 402 and carries the Bazaar extension, and gives a simulated accept or reject decision. It performs no payment and does not index the resource, so a seller can see the result of the setup before the first paid call.
2. x402scan and directories
x402scan indexes a domain's x402 endpoints from its OpenAPI file once the domain is registered there. agentic.market is the human view of the Bazaar. Directories such as nohumans.directory list endpoints and can run paid test calls against them. Each index is read by a different set of agents, so being in several of them widens the set that can find the endpoint.
3. Write the description for the search box
Bazaar search is text matching on the listing's description. A description that starts with the task in plain words, such as 'Which x402 API should my agent call for this task?', matches queries that a brand name does not. Agents match on the words they type.
Coinbase recommends explicit input schemas and output examples for any route that takes parameters; without them an agent can find the endpoint but cannot construct a valid call. The price and network are part of the description an agent reads.
A free way to see what agents see
Ontario's Bazaar readiness check runs one public buyer task against the Bazaar search and reports whether the endpoint is returned for it, together with the observable blockers in its 402 response and metadata. It is free, it does not pay the endpoint, and its result is not Coinbase certification.
Take the next step
The pages below go deeper on this question.
Sources and observed evidence
Continue reading
Publish an x402 API profile with a readiness report and badge
Prepare your x402 API for agent discovery: validate free, inspect readiness evidence, then publish an Ontario service profile for 0.50 USDC only when you need it.
MCP Registry, Smithery or Bazaar: build the agent purchase path
Separate MCP installation from paid API discovery. Give agents a callable tool, free preflight, explicit payment requirements and evidence of fulfilled output.
Can x402 payments be refunded?
An x402 payment is a USDC transfer that is final once it settles, so a refund is a voluntary new transfer and the real protection is a seller that settles after the result exists.
How big is the x402 market?
Coinbase's Bazaar index lists tens of thousands of paid endpoints, but most show one or two payers in 30 days, and repeat demand sits in a few categories.
Are cheaper x402 APIs worse?
Not necessarily; price rarely decides which x402 API agents use, as a reseller that charges more than the original search API and gets more calls shows.
Do Claude or ChatGPT pay for MCP tools?
Claude and ChatGPT can call MCP tools, but neither pays for one by itself; a paid MCP tool needs a client wrapper with a funded wallet and a spending limit.
Which networks does x402 support?
x402 is network-agnostic; Coinbase's facilitator settles on Base, Solana, Polygon, Arbitrum, Monad and World, and most paid traffic today is USDC on Base.
How do I know an x402 endpoint is legit?
Three observable checks show whether an unknown x402 endpoint is live, priced as listed and used by repeat buyers; Ontario's finder runs them for 0.005 USDC.