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A Notion Custom Agent can browse the Nevermined Catalog and pay for services as it works. You add one MCP connection, paste your Nevermined API key, and the agent does the rest. This is the per-host walkthrough; for the full tool surface and the safety model, see Using the Catalog from a harness.
Notion connects with a plain Nevermined API key, not the OAuth “approve a spending cap” flow that some assistants (Claude, ChatGPT) use. The key is your credential — it spends whatever its Nevermined account funds, so you set the budget on your account, not in Notion.
Custom MCP connections are a Custom Agents feature on Business and Enterprise plans only, and a workspace admin must enable custom MCP servers and approve the server URL before an agent can use it. They don’t apply to the default Notion AI.

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Before you connect

1

A Nevermined account

Free, at nevermined.app.
2

A Nevermined API key

Create a plain API key in the app — Settings → Global NVM API Keys — for the environment you want, and send the whole string, prefix included (sandbox:… or live:…). A key minted by an OAuth flow can’t pay through the Router’s delegation routes, so use a plain one. See Get a Nevermined API key.
3

A way to pay

The key spends from one of two budgets you set up once: a Nevermined Subscription whose monthly credits a plain key can spend, or a spending delegation — a capped, revocable budget funded from your own wallet (Using the Catalog from a harness walks through it). Discovery is free and needs neither.
Start on sandbox, where you use testnet funds and nothing costs real money, before you point the agent at live.

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Add the Catalog to your Custom Agent

1

Admin: approve the server (once)

A workspace admin enables custom MCP servers and approves the Catalog URL in Settings → Connections. Approve the URL for the environment you want:
2

Add the connection to the agent

In your Custom Agent, open Settings → Tools & Access → Add connection → Custom MCP server, enter the same URL and a display name.
3

Authenticate with your key

Choose the header-based (API key / bearer token) sign-in, paste your Nevermined API key, and Connect.
Rehearse on sandbox first. The Catalog MCP accepts only the exact header Authorization: Bearer <key>; if the connection sends your key in another shape, calls look connected but never pay — if that happens, ask for a free discovery call and confirm a paid one actually charges before trusting it on live.

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Your Nevermined API key

That key is your credential — there is no separate consent screen to approve. Keep the prefix: a live: key for mcp.live, a sandbox: key for mcp.sandbox. The key spends whatever its account funds — your Subscription credits, or a spending delegation funded from your wallet — so the budget and the audit trail live on your Nevermined account, not in Notion. Treat it like a password: never commit it or paste it into a shared chat. Every way to mint one: Get a Nevermined API key.

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Make your first paid call

Ask for something only live data can answer, and name the connection so the agent reaches for it rather than answering from memory.
1

Browse for free

Ask the agent to “list the Nevermined catalog categories” — a free tool call, no payment.
2

Ask it to buy

“Buy the service with slug <slug> through the Nevermined connection and show me the response.” The paid call draws on your subscription credits or delegation and returns the merchant’s response.
If the agent answers without paying, it answered from its own knowledge — name the connection and ask for live data. More on phrasing: Catalog MCP tips.

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Disconnect or rotate the key

  • Stop the credential (Nevermined side). The key is the credential, so to cut the agent off, rotate or delete the key in the app (Settings → Global NVM API Keys) — every call with the old key then fails. To cap spending without revoking the key, revoke the delegation it spends from in Payment methods; discovery still works.
  • Remove the server (Notion side). Remove the connection from the agent’s Tools & Access; a workspace admin can also remove the approved server in Settings → Connections.
To spend again, paste a fresh key; if you revoked the delegation, create a new one — see Using the Catalog from a harness.

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Next

Using the Catalog from a harness

The full plain-key playbook — discovery, delegations, and the safety rules.

Catalog MCP — full reference

Every tool, the API-key header, and every refusal code.