A few days ago I posted about a problem I hit with MCP tool schema drift. The short version: An MCP server changed a parameter from location to city . My agent kept sending location . Nothing warned me before runtime. That first version of MCP Sentinel was just the basic idea: sentinel init sentinel snapshot sentinel check sentinel diff Enter fullscreen mode Exit fullscreen mode Since then, I shipped MCP Sentinel v1.0.0 . GitHub: https://github.com/Wannavf/mcp-sentinel Enter fullscreen mode Exit fullscreen mode npm: npm install -g @wannavf/mcp-sentinel Enter fullscreen mode Exit fullscreen mode The framing changed a bit The original problem was annoying because it broke my tools silently. But after feedback, I think the bigger point is this: MCP tool schemas are contracts. If a tool changes its parameters, required fields, enum values, return shape, or descriptions, that is not just a small implementation detail. It changes what an agent can ask for.…