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Web AI assistants — Claude.ai, ChatGPT, LangSmith Fleet — can browse the Nevermined Catalog and pay for services as they work, without you ever handing over an API key. You paste one URL, approve a single spending cap, and the assistant does the rest. This is the no-code, in-the-browser counterpart to Using the Catalog from a harness.
This is the buyer side — giving an assistant you already use a wallet. Driving the Catalog from your own code or a coding agent? See Using the Catalog from a harness. The exhaustive per-host click paths (name warnings, Fleet’s OAuth provider table, every refusal code) live on the Catalog MCP page — this page is the walkthrough that gets you there.

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See it in action

Give an assistant a budget and ask it to go and buy what it needs — a search, a page fetch, a live forecast — and it pays per call, for a few cents, against a cap you set.

Your AI assistant can now pay for things.

The per-assistant walkthroughs are below, and collected on the Catalog videos page.

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What you get

  • No API key, no client secret, no vendor account. Claude and ChatGPT discover everything from one URL; Fleet takes the endpoints once.
  • One consent screen sets who can spend, how much, and for how long. The grant is the credential — your assistant never holds a key.
  • Every payment is on the record — merchant, amount, transaction hash, and what’s left of the cap — in your payment ledger.
  • Your assistant can pay any service it discovers, not a fixed list you wire up in advance.
  • Revoking is instant and self-service, from Connections in the Nevermined app.

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How it works — three moves

1

Point your assistant at one URL

The Catalog MCP server URL. In Claude and ChatGPT that’s the whole configuration — paste it, leave the OAuth client ID and secret empty, and the assistant discovers the rest. LangSmith Fleet doesn’t discover, so you enter its endpoints once.
2

Browse the Catalog for free

Discovery needs no sign-in. Ask for the categories, search for a service, read its price — all before you approve anything.
3

Approve a spending cap, once

Nevermined’s consent page opens: check the Sandbox / Live badge, set the cap and how long it’s valid for, then Grant access. That approval is a commerce grant — it spends only from the budget you just approved, only through the Router, and you can revoke it any time. Your assistant retries the call it was blocked on.
Ask in a way that makes the assistant reach for the Catalog. All three will happily answer from their own knowledge and charge nothing — which looks like a broken connector and isn’t. Name the connector in the prompt (“using the Nevermined connector, …”), ask for something only live data can answer, and name services in single words. More on phrasing in the Catalog MCP tips.

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Pick your assistant

The click paths differ; the mechanics underneath are identical. Each tab has the short version and a link to the full walkthrough.
1

Add the connector

Settings → Connectors → Add custom connector. Name it and paste the server URL. Leave the OAuth client ID and secret empty — Claude identifies itself to Nevermined on its own, so there’s nothing to register.
2

Ask for something free, then ask it to buy

Enable the connector and ask “list the Nevermined catalog categories” (no sign-in). Then ask it to buy a service — the paid call returns 401 and Claude shows an inline Connect card.
3

Approve the cap

Connect → the consent page opens. Set the cap and validity, Grant access, and Claude retries the call with the grant.

Connect to the Catalog from claude.ai.

Full click path: Catalog MCP → Claude.

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Which URL to point at

Fleet needs the mcp.api. host so it’s challenged for auth on connect; Claude and ChatGPT use the plain host and are prompted when they first try to pay. One screen, and it’s the only place a human is required. You set the spending cap (in USDC or EURC) and how long the grant is valid for. The environment badge (Sandbox or Live) and who is asking are shown, not chosen. Before you grant, know that:
  • On Live, the cap is real money.
  • The assistant may pay any service it can reach, not a fixed list.
  • Nevermined’s routing fee comes out of the same cap — the cap is the total debited, not what merchants receive.
  • The grant also lets the assistant read your payment history and wallet balance. The cap bounds what it can spend, not what it can see.
Granting creates a budget confined to that cap and window, funded from your own wallet, and hands the assistant a credential that spends only through it — never a card mandate. Full breakdown of the consent screen: Catalog MCP → What the consent page asks. What happens once the cap is spent or the window ends: When the grant runs out.

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Revoke any time

Open Connections in the Nevermined app and disconnect the assistant — the credential stops working on its next call. To spend again after that, or after a cap is used up, re-run the connect step and approve a new cap; a budget is never widened or extended in place.

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Next

Catalog MCP — full click paths

Every step for Claude, ChatGPT and Fleet, the consent details, and every refusal code.

Using the Catalog from a harness

The code-free playbook for driving discovery and payment from your own agent or coding harness.

Catalog videos

The connect walkthroughs for each assistant, plus the Catalog overview and outcome examples.

Router: pay

Delegations, the spending cap, the rails, and every refusal code.