MCP is useful, but most of the time you do not actually need it. It gives an agent a clean way to discover tools, call APIs, and work with external systems. In practice, a skill file can describe the same usage path without dragging the whole MCP surface into context.
But MCP is not free; rather than MCP itself, the real issue is the habit of loading a big MCP surface into every session, no matter what the session is actually about. Once a Claude Code or Codex run pulls in a bunch of servers, the model sees those tool definitions right away, even if the job is just writing docs or fixing a small bug. That is where the waste starts.
The hidden cost of always-on MCP
Every MCP server brings metadata with it: tool names, descriptions, argument schemas, nested parameters, enums, examples, and sometimes prompts or resources. While useful, this is still context.
If you connect a handful of lightweight tools, the overhead is annoying but manageable. If you connect a real stack of services, the cost compounds fast.
