Labsco
MCP SERVER

Put one word in front of any MCP server command and its JSON responses shrink by roughly half before they reach the model.

MCP Plumbing: Proxies, Registries & Inspectors
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