MCP Connection

Call a tool on a connected MCP server — you pick which, Plooi does the rest.

In Connection, tool, JSON arguments · Out Tool result · Cost Free

What it does

Calls a tool on an MCP server you have connected. You pick the connection, pick a tool the server itself reports, and pass it JSON arguments; the answer lands on the card and travels on to the next method.

⚠ It is MCP now — and for two years it was not

This block shipped as “MCP Client” and described as speaking the Model Context Protocol. It did not: what went over the wire was a plain POST from your browser to a URL you typed. A real MCP server answers that with an error.

#1056 renamed it to “HTTP Tool Call” rather than half-build the real thing, and that name was honest — a browser cannot open MCP sessions against arbitrary servers (CORS), and routing them through a backend means fetching user-supplied URLs from our infrastructure.

Both of those were solved separately, so #1370 finished the job. The call now runs server-side over JSON-RPC 2.0 with a real initialize handshake, tools/list and tools/call — and #1372 added the sign-in flow the tools that need one expect.

Worth knowing

You never type a server address here. Connections live under Settings → Connections, and the address belongs to the connection, not to the card — which is also why your credential never reaches your browser.

Some tools hand you a token to paste; others sign you in at their own site and send you straight back. Either way Plooi holds the credential server-side and never sees your password.

The tool list comes from the server itself, so it is always what that server actually offers rather than what someone wrote down. A failed call shows as a failure: since #1056 an unreachable server is no longer stored as a successful result, error text and all.