What
Failures from MCP servers are now classified as downstream_error, downstream_unreachable, user_auth, user_config or other and attached to tool-error telemetry, so it is possible to tell a server that is down from a login or config problem. Nothing you see changes.
Details
- Classification uses error classes, JSON-RPC and HTTP codes, and a curated set of network error codes including ECONNREFUSED, ERR_PROXY_TUNNEL and ESOCKETTIMEDOUT, following up to four chained causes.
- The classification is also attached to "MCP server is not connected" and MCP tool timeout errors.
- MCP connect telemetry gained flags for a suppressed listen and a denylisted negotiation.
Evidence
downstream_unreachable, mcpErrorSource
Strings lifted out of the shipped bundle, so the claim above can be checked against them.