# mcp.server.describeStartupFailure

- **Module:** mcp.server
- **Package:** @libtmux/mcp
- **Language:** TypeScript
- **Kind:** function
- **Source:** https://github.com/libtmux/libtmux-ts/blob/3fe1ca654b81b8cbf4a13b777a001a3298c87a6f/packages/mcp/src/server.ts#L301
- **Page:** https://libtmux.org/en/ts/latest/mcp/reference/mcp-server-describestartupfailure/

```
mcp.server.describeStartupFailure(error: : unknown, environment: : Readonly<Record<string, string | undefined>> = process.env) -> string
```

One actionable line for a failure that happened before serving began.

stdout is the protocol, so stderr is the whole diagnostic channel, and an MCP
client surfaces it as the reason a server would not start. `spawn`/`ENOENT`
is separated because Node reports it as `spawn tmux ENOENT`, which reads as
tmux refusing rather than tmux being absent.