The median MCP server costs 3,150 tokens before your agent calls anything

Every MCP server you connect sends its full tool list to the model before the model does anything. You pay for that list on every single turn, whether the agent uses one of those tools or none of them.

I had a rough sense this was expensive. I did not have a number. So I went and measured it.

The method

The MCP directory I maintain has about 10,500 servers with a remote HTTP endpoint. I took a random 60, sent each an unauthenticated tools/list, and measured the JSON that came back.

import json, subprocess