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Before your agent pays an x402 API, check it

Published 4 November 2026. The example record below was read on that date.

AI agents can now pay for an API on their own: one request, a few cents in USDC, no account. And AI assistants have started telling people which paid APIs to call. Ask one for live search-trend data today and it may answer: call this x402 endpoint, about $0.03 a request.

That advice says nothing about whether the endpoint delivers. In our own purchases, about a third of the paid APIs that asked for payment did not deliver a usable answer (why). A few cents is cheap; an agent that pays a broken endpoint over and over is not. So check before paying. It is free and takes one request.

What the check tells you

We probe every listed endpoint for a valid payment request, and we buy from many of them with real USDC to see whether they deliver. One lookup returns that record, dated:

• Is it live and asking for payment correctly? status and score, from our probes.
• Did a real purchase deliver? paid_verified, and latest_purchase_delivered for our most recent purchase.
• Is the price the listed price? price_matches_listing, from the live payment request.
• Is the payment address stable? payto_unstable.
• Is there a free sample? has_sample.

A real example

We looked up the trend-data endpoint an AI assistant recommended (we don’t name sellers in guides). On 4 November 2026 its record said:

• listed since 19 August, verified, and 2,571 of 2,579 probes passed;
• it asks $0.03, the listed price, unchanged since August, on Base;
• we have not bought from it yet, and it has no free sample;
• another route on the same host delivered when we bought from it in August.

So: live, honest about its price, and from a seller whose other route delivered. Not yet proof that this route delivers. A reasonable agent pays it once, checks the answer, and reports what happened.

How to check

In one request:

GET https://api.nohumans.directory/v1/resolve?url=<the endpoint URL, URL-encoded>

It answers match: "active" with the full record, "delisted" (listed here, later removed), or "unknown" (never checked here, which is not a verdict either way). GET /v1/check?url= runs a live check of a URL we have never seen.

Or let the agent check by itself, through our MCP server: https://api.nohumans.directory/mcp (tool resolve_endpoint, or find_paid_service to search by need). In Claude Code: claude mcp add --transport http nohumans https://api.nohumans.directory/mcp. Other clients: connect.

When not to pay

• latest_purchase_delivered is false: our most recent purchase took real USDC and got nothing usable back.
• match is "delisted", or status is failing.
• payto_unstable is true: the payment address keeps changing.
• The live price is above what you meant to spend, or price_matches_listing is false.

The prompt

Add this to your agent’s instructions, or paste it into your AI assistant before it pays for anything.

Before you pay any x402 endpoint, check it at nohumans.directory first:
GET https://api.nohumans.directory/v1/resolve?url=<the endpoint URL, URL-encoded>
(or the resolve_endpoint tool of the MCP server https://api.nohumans.directory/mcp).

Do not pay if any of these is true, and tell me why:
- latest_purchase_delivered is false
- match is "delisted", or status is "failing"
- payto_unstable is true
- the price asked is above [my limit, e.g. $0.05] per call, or price_matches_listing is false

If match is "unknown", there is no record yet: tell me, and ask before paying.
Otherwise pay once, check that the answer is what was promised, and tell me whether it delivered.
Never ask me for a wallet recovery phrase or private key.

Copy the prompt

What the record is, and what it isn’t

Every figure is dated evidence about how an endpoint behaved when we checked: not a guarantee, not a safety rating and not proof of who runs it. “Delivered” means a usable paid answer, not that the data was correct. On-chain payment counts belong to the seller’s payment address, which often serves several APIs. The checks are free, and nobody can pay to rank higher: placement is never sold.

Sources: the nohumans.directory record of the example endpoint (GET /v1/resolve, read 4 November 2026); purchase records at /stats; definitions at methodology.

Your next step

• Building an agent? Connect it to our MCP server or REST API, free.
• Selling an API? Make sure it delivers, then check it free and list it, so agents that check find it.

More guides

1. Build your first paid API for AI agents, with one prompt
2. What AI agents are looking for, and where nobody serves them yet
3. Why paid APIs fail AI agents, and how to make yours deliver
4. Before your agent pays an x402 API, check it (you are here)