mcp servers don't validate tool responses match declared schema

tested mcp sdk 0.5.0 yesterday and the servers dont validate that tool responses actually match the schema you declared at registration. you can declare a tool returns {"status": string, "count": number} but if it returns {"status": "ok"} with count missing the sdk just passes it to the agent without validation. this breaks downstream agent logic that assumes the schema contract is enforced. we had to add response validation middleware that checks every tool output against the declared schema before passing to the agent