As of May 2026
My LLM session loaded 276,989 tool-schema tokens before I typed anything. Eleven MCP servers, 609 tool definitions, 27.7 percent of a million-token window spent on tool payload the model might never call.
A bigger context window did not fix that. It gave the problem more room. The fix was not more context, it was loading less of it until the task actually needed it.
Tool loading is context architecture. The schemas you load before the first prompt are a design decision, and most agents make it by accident.
The broker pattern, applied to MCP
So I built mcp-broker, PgBouncer for MCP. The agent sees four broker tools: search_tools, describe_tool, call_tool, and status. The upstream MCP servers still exist, but their full schemas load only when the task needs them, instead of front-loading every definition into the window before the session has a single instruction to act on. The thin stable interface sits at the front, and the brokered complexity stays behind it until something asks.
Measured on my own setup on 24 May 2026, the always-loaded tool definitions dropped from 609 to 43, a 92.94 percent cut. The serialized tool tokens fell from 276,989 to 45,281, down 83.65 percent. The tool payload share of the window went from 27.7 percent to 4.5 percent. Your numbers will differ depending on how many servers you run, and that is the point: the ratio is the lesson, not the absolute figure.
What it ships as
mcp-broker is open source under the MIT license. Version 1.1.0 is published on PyPI, Homebrew, NPM, Docker Hub, GHCR, and the MCP Registry. The release gate includes coverage and a 100 percent mutation score, because a broker that sits in front of every tool call is not a place to be loose about correctness.
Before I typed
276,989
tool-schema tokens loaded before the first prompt - 27.7 percent of a million-token window.
The payload
609 tools
eleven MCP servers and 609 tool definitions, most of which the model would never call.
After the broker
4.5%
tool payload share fell from 27.7 to 4.5 percent, with 609 always-loaded tools cut to 43.
