NBB Annual Accounts MCP

Setup guide

Claude Code

One command. Claude Code speaks streamable HTTP natively and can send the header.

You need a key first. Your account page issues one — it starts with nbb_live_ and is shown once. If you have not signed up yet, sign in with your email address; the free plan needs no card.

Add the server

In a terminal, with your key pasted in place of nbb_live_…:

claude mcp add --transport http nbb https://uat.nbb-mcp.be/mcp --header "Authorization: Bearer nbb_live_…"

That registers it for the current project. Add --scope user to have it available in every project on this machine: 

claude mcp add --scope user --transport http nbb https://uat.nbb-mcp.be/mcp --header "Authorization: Bearer nbb_live_…"

Confirm it registered

claude mcp list

nbb should appear with a connected status. Then start Claude Code and check /mcp in the session: it lists the three tools (search_company, get_annual_accounts, get_operation).

Your key ends up in Claude Code's configuration file in plain text, like every other MCP credential. Treat it as a secret in a dotfile: do not commit a project-scoped .mcp.json containing it to a shared repository — use --scope user instead.

Check that it works

Start a new conversation and ask:

Find the annual accounts of Colruyt

The assistant should call search_company, find enterprise number 0400.378.485 (Etn. Fr. Colruyt NV), then call get_annual_accounts, poll get_operation once or twice, and read back a balance sheet with rubric codes.

It says it has no such tool

The connector is not loaded. Most clients only pick up MCP servers at start-up: restart it, and check the server is enabled in the client's tool list.

It reports 401 or "invalid API key"

The header is missing or the key is wrong. The value must be the whole key including the nbb_live_ prefix, after the word Bearer and one space. Keys are shown once — if you did not copy it, regenerate on your account page.

It gives up after one call and says it is still pending

get_annual_accounts is asynchronous: it returns an operation id and a poll_after_seconds. Tell the assistant to poll get_operation until the status is completed. The tool descriptions say so, but a smaller model sometimes needs the nudge.

Removing it

claude mcp remove nbb

Other clients