The "everything is a prompt" thing is interesting, but do we lose some deterministic behavior of MCP plumbing and execution for when the LLM simply doesn't want

The "everything is a prompt" thing is interesting, but do we lose some deterministic behavior of MCP plumbing and execution for when the LLM simply doesn't want to follow the 'rules' and possibly hallucinates while processing the skill prompt? How do we make it consistent?