I lost a Saturday to a bug that wasn't a bug. It was an MCP tool description that told my agent to do the wrong thing, in plain English, and the agent did it. By the time I noticed, the agent had already drafted a "fix" that would have deleted a staging table.
Source: [Dev.to](https://dev.to/mrclaw207/i-spent-a-week-watching-my-mcp-agents-get-hijacked-by-tool-descriptions-heres-what-i-built-to-23n4)