I checked every MCP server in the official registry. About 1 in 10 is broken.

A developer found that about one in ten remote MCP servers in the official registry is genuinely broken, contradicting a widely repeated claim that half are dead. The 'half' figure likely comes from counting servers requiring an API key as down. The developer warns that uptime checks miss the more critical issue of schema drift.

There is a number going around that roughly half of all remote MCP servers are dead. I had repeated it myself, in the README of a tool I published. I could not find where it came from, so I measured it. The answer is that about one in ten is actually broken. The "half" figure appears to come from counting servers that require an API key as if they were down. Here is the method and the full breakdown. On 29 July 2026 I pulled every entry from the official MCP registry https://registry.modelcontextprotocol.io — 1,200 servers. Of those, 297 had status: active and advertised a remote endpoint URL the rest are stdio/local packages with nothing to probe over the network . Each got one anonymous JSON-RPC initialize over streamable HTTP, with a 10 second timeout: { "jsonrpc": "2.0", "id": 1, "method": "initialize", "params": { "protocolVersion": "2025-06-18", "capabilities": {}, "clientInfo": {"name": "mcp-uptime", "version": "0.1.0"} } } Then I classified the response: a valid result containing protocolVersion or serverInfo is up, 401/403 is auth-gated, and everything else got bucketed by its actual failure. | Result | Count | Share | |---|---|---| | Completed an MCP handshake | 133 | 44.8% | | Auth-gated 401/403 | 134 | 45.1% | | DNS failure | 8 | 2.7% | | Server error 5xx | 6 | 2.0% | | Not found 404/410 | 5 | 1.7% | | Redirect 307/308 | 4 | 1.3% | | Timeout | 2 | 0.7% | | Non-MCP response | 2 | 0.7% | | Other 400, 405, connection | 3 | 1.0% | Reachable: 267 89.9% . Genuinely broken: 30 10.1% . Look at the first two rows. 55.2% of these endpoints will not complete an anonymous handshake — and that is suspiciously close to the number people quote. But 134 of those 164 are returning a clean 401 or 403. They are running. They are answering. They want an API key, which is a completely reasonable thing for a hosted service to want. Counting those as dead inflates the failure rate by roughly five times. This matters beyond pedantry: if you believe half the ecosystem is rubble, you build defensively against the wrong thing. The actual failure distribution is a small tail of genuinely dead hosts — mostly DNS that no longer resolves , which is the signature of an abandoned demo rather than a flaky service. Liveness is the easy question, and it is not the one that will hurt you. A server can return a perfect handshake and still break every agent that depends on it, because what agents actually consume is the tool contract : names, descriptions, and input schemas. Rename a tool, add a required parameter, tighten an enum — the endpoint stays green and your agent fails at call time, mid-run, looking for all the world like a model error. Downtime is loud. Schema drift is silent, and it surfaces as "the AI is being weird today." So an uptime check that pings a URL is measuring the least interesting property available. What you want to watch is whether the tool inventory and schemas changed since the last time you looked. The sweep is about sixty lines: page through /v0/servers , keep active entries with a remote URL, POST one initialize , bucket the responses. If you run it and get materially different numbers, I would genuinely like to know. I also published the checker as a free tool — it does the handshake, the tool inventory, and the schema-drift comparison, as a live MCP server https://mcp-uptime.park11innyc.workers.dev/mcp io.github.park11innyc-lgtm/mcp-uptime in the registry and as an Apify Actor. No auth, no cost. I published a number I had not verified, in a README, on a public page, about the exact domain the tool claims expertise in. That is the same mistake I keep writing about from other angles: trusting a status field instead of the artifact https://dev.to/parkerrrrr/published-is-not-deliverable-what-five-storefront-apis-dont-tell-you-412h , and the operational parts of MCP that tutorials skip https://dev.to/parkerrrrr/the-parts-of-building-an-mcp-server-that-the-tutorials-skip-3n07 . A widely-repeated statistic is a status field. It feels like knowledge and it is actually someone else's unverified claim, forwarded. Measuring it took under an hour.