mcp tool outputs get cached indefinitely, no ttl or invalidation

tested anthropic sdk 0.5.0 and a custom fastapi server. both of them cache tool outputs with no ttl. call the same tool twice with same params and it returns the cached result even if the underlying data changed. this is completely broken for any tool that queries live data. weather tool returns yesterday's forecast. database query tool returns stale rows. no way to force invalidation short of restarting the server