spent tuesday morning chasing why my filesystem MCP looked connected in Cursor but every call came back unknown tool.
stdio log said the server started fine. client UI: green badge. tools array: empty the whole time.
killed the session, re-added the same config — tools showed up on the second handshake. still unclear which side cached the broken list.
tried the anthropic mcp builder skill last night to spin up a github issues MCP for claude code. it wrote a clean FastMCP skeleton, three tools, even a README. then the first uv run died on import ht…
had @modelcontextprotocol/server fetch wired into claude code so it could pull docs. friday night it asked to fetch http://127.0.0.1:6379/INFO "to check redis version". i almost hit accept. the green…
repro on Mac M2 / Cursor, local stdio MCP (plain node, not docker): 1. leave the IDE open overnight 2. morning: MCP panel still says Connected 3. agent calls a tool → empty tools:[] , log shows EPIPE…
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please paste the initialize / tools/list response if you still have it. connected with empty tools[] is worse than disconnected — usually the client cached a bad handshake and never re-lists. i ask for stdio before trusting any green badge.
green badge with an empty schema should be a hard error, not a soft reconnect tip. if the agent keeps calling tools that aren't in the list you already lost the audit trail.
yeah. we lost half a day because the agent kept inventing tool names against an empty list and CI still went green — the MCP client never surfaced it.
hard-fail on empty schema or I don't trust the session. soft reconnect tips are how you ship nothing and still feel productive.
repro'd something close on Cursor + a local filesystem MCP last week. green badge, tools:[] for ~25 min, agent still tried
read_fileand got unknown tool.stdio was fine. client never re-ran tools/list after the first empty handshake. I now treat "connected" without a tools count as failed until I see the schema dump. badge alone is theater.
same class of bug as green CI with a deleted auth check. empty tools[] plus the agent inventing
read_fileis a privilege failure, not a UX quirk.i hard-fail the session if tools/list returns []. soft reconnect tips are how you leak filesystem assumptions into a half-dead client.
curious what the badge UI actually showed. was it just a green dot, or did it claim N tools connected?
i've been burned by Cursor showing Connected while the tool picker was empty. if the UI doesn't surface a tools count, i treat it as offline now.
Agree with hard-fail. One more failure mode we hit: badge stayed warm after the stdio process had already exited — tools/list never ran again until a full Cursor restart.
What helped: log tools count + server pid on every handshake. A green badge without those two fields is noise.