Name: GCF Proxy
Author: blackwell-systems

LABSCO SUMMARY

A one-line config change, and you can measure whether it paid off.

The verbose flag prints per-call bytes in and out and a session total, so this is testable rather than a claim: run it against a server you already use and read the numbers. The published benchmark for a yfinance session is 117.8KB of JSON reduced to 63.4KB. If you control the server, the author points you at the GCF libraries directly instead, for better control over deduplication and delta encoding.

What it is

A bidirectional proxy that re-encodes structured JSON as GCF on the way out and decodes GCF back to JSON on the way in. Neither the server nor the client changes: you prefix the existing command with gcf-proxy and everything else stays as it was.

What you get

Structured tool responses re-encoded to a denser format, with per-call savings logged to stderr under --verbose and a session total at the end
GCF appearing in tool call arguments is decoded to JSON before the server sees it — detection is a 4-byte prefix check, and non-GCF strings pass through untouched
Local servers by prefixing the command; remote ones with --upstream pointing at a Streamable HTTP endpoint, with session id tracking handled automatically
--http turns the proxy itself into a remote Streamable HTTP server, with a health check at /health
--session deduplicates previously-transmitted symbols, --cache reuses encodings for identical calls, --delta sends only what changed
--no-flatten uses the expanded encoding for nested objects, which open-weight models currently read better
--min-size skips encoding for small responses, defaulting to 100 bytes, and --stats-file writes JSON stats after each call

Requirements

One install, three ways: pip install gcf-proxy, npm install -g @blackwell-systems/gcf-proxy, or go install github.com/blackwell-systems/gcf-proxy@latest. Then change the command in your MCP config to gcf-proxy and move the original command into args. Nothing else — no key, no server change. The published npm package is @blackwell-systems/gcf-proxy, version 0.10.2, and the Python package is gcf-proxy, version 0.10.1. MIT licensed.

Setup effort

One command — pip install gcf-proxy

See installation options

USE CASES

01

Cutting the cost of a chatty server

Prefix its command with the proxy and read the savings on stderr before deciding to keep it.

02

Shrinking a server you cannot modify

Get the reduction without touching a third-party binary or another team's code.

03

Doing the same for a remote server

Point the proxy upstream at the HTTP endpoint rather than spawning a subprocess.

04

Working with an open-weight model

Switch off flattening so nested objects arrive in the form those models read more reliably.

BEFORE YOU INSTALL

What to know first

Requires

gcf-proxy on PATH

INSTALLATION

Connect your client

Add the block to your client, or run the command directly.

Server setup

Configuration file

JSON

{
  "mcpServers": {
    "memory": {
      "command": "gcf-proxy",
      "args": [
        "npx",
        "-y",
        "@modelcontextprotocol/server-memory"
      ]
    }
  }
}

pip

TERMINAL

pip install gcf-proxy

GCF Proxy