How do I check whether my MCP server is connected in Claude Code?

Run /mcp inside Claude Code. It lists the servers it knows about and their connection state. If your server is not in that list at all, the configuration was never read — that is a different problem from a server that is listed but failing.

Why does my MCP server work when I run it manually but not in Claude Code?

The most common cause is a relative path. Claude Code may launch the server from a different working directory than your shell, so a command like node ./dist/server.js resolves to nothing. Use an absolute path. The second most common cause is that your shell has environment variables the launched process does not.

Do I need to rebuild my MCP server after changing it?

If it is TypeScript, yes. Claude Code runs the built output, so an edit to src/ that has not been compiled to dist/ changes nothing. A server pointing at a dist file that does not exist yet fails to start with no obvious message.

Why does my MCP server connect and then immediately drop?

Usually the server crashed on startup — a missing environment variable, a failed import, or a port already in use. For stdio servers, anything written to stdout that is not protocol traffic also corrupts the stream. Debug prints belong on stderr.

My MCP server will not connect in Claude Code

Almost never the protocol. Almost always a path, a missing build, or a server that dies on startup and says so where nobody is looking.

Last updated: 2026-09-22

Check this first

Inside Claude Code, run /mcp. That tells you which of two problems you have, and they have nothing to do with each other:

What you see	What it means
Your server is not listed	The configuration was never read. Nothing about your server code matters yet
Listed, but failing or disconnected	The configuration was read and the server was launched. Now it is a startup problem

People usually skip this check and start rewriting the server. Half the time the server was never launched.

If it is not listed

Confirm the config is where you think: an .mcp.json in the project, or whatever claude mcp add wrote.
Confirm the JSON parses. A trailing comma fails silently and looks exactly like nothing happening.
Restart Claude Code. Configuration is read at startup.

If the file parses and the server still is not listed, check the scope before anything else: claude mcp add defaults to --scope local, which writes ~/.claude.json and not the .mcp.json you are looking at. The .mcp.json that travels covers which scope goes where, and the credential names that expand to an empty string on purpose.

If it is listed but will not start

In order of how often each one is the answer:

#	Cause	How to tell	Fix
1	Relative path	Works in your shell, not in Claude Code	Use the absolute path to the entry file
2	Not built	Config points at `dist/`; you have only edited `src/`	Run your build, then retry
3	Crashes on startup	Connects then drops immediately	Run the exact command from the config by hand and read the error
4	Missing environment variable	Your shell has it; the launched process does not	Put it in the server's `env` block in the config
5	Something printed to stdout	Garbled or immediately-closed connection on a stdio server	Send every log line to stderr; stdout is the protocol

The test that settles it

Run the server's command yourself, exactly as the config has it — the same absolute path, the same arguments:

node /absolute/path/to/your-server/dist/server.js

If that errors, you have your answer and it was never a Claude Code problem. If it sits there waiting, the server is fine and the problem is the configuration above it.

A working reference helps more than any checklist. kit-one-tool-mcp is one tool with 15 offline tests — clone it, run npm test, and you have a known-good server to compare against. If it connects and yours does not, the difference is in your config, not in the protocol.

What does it cost to have someone set this up?

Flat prices, written scope, stop at any rung. No call to book, no retainer.

Rung	What you get	Clock
Free — starter repo	A real setup you copy yourself	now
$29 — Setup Lite	One project: CLAUDE.md, allowlist, one skill, as a pull request you review	24 hours
$99 — Setup Sprint	3–5 skills, hooks, up to 3 MCP servers, plus a runbook	48 hours
$79 — Surface Audit	Already set up and still fighting it: contradictions and an exact fix list	48 hours

Setup Lite $29 Or start free

Clocks run from a complete intake, not from the Stripe receipt.