GCF

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Codex Plugin ​

One-command install to save 71% on MCP tool call tokens in OpenAI Codex.

Install ​

bash
codex plugin add gcf-proxy

What it does ​

The plugin adds two skills and a stats hook:

ComponentDescription
/gcf-proxy:setup <server>Wrap any MCP server with gcf-proxy
/gcf-proxy:statsShow token savings for the current session
Stop hookNotification after each turn showing calls rewritten and tokens saved

Quick start ​

After installing, wrap any MCP server:

/gcf-proxy:setup github

This modifies your MCP config to route the server through gcf-proxy. The original config is preserved (disabled, with a -raw suffix) so you can revert anytime.

How the savings work ​

  1. First call (71% savings): GCF encodes the same structured data in 71% fewer tokens than JSON. The model reads GCF natively with 100% comprehension accuracy.

  2. Subsequent calls (up to 92%): Session deduplication detects repeated structure across tool calls. Only deltas are transmitted. By the 5th call, token usage drops to 8% of JSON.

  3. Zero code changes: The proxy wraps any MCP server. The server still outputs JSON; the proxy re-encodes before it reaches the model.

Session stats ​

The plugin writes stats to /tmp/gcf-proxy-stats.json after each tool call rewrite. The Stop hook reads this and shows a notification:

gcf-proxy: 12 tool calls rewritten, 68% fewer tokens (~4.2K tokens saved)

Disable the notification anytime via /hooks in Codex.