Why Schema Drift Is the Silent Killer of MCP Deployments

Schema drift in MCP deployments causes silent failures because agents read schemas at runtime without a compile step. A field renamed from customer_id to account_id or a float-in-dollars parameter changed to integer-in-cents produces well-formed but semantically wrong calls. JSON Schema validates shape, not intent, so no signal flags the mismatch. Teams must version schemas explicitly, log schema versions with every tool call, and treat MCP tool schemas as public API contracts.