gcf-codex-plugin
June 13, 2026 ยท View on GitHub
Codex plugin for GCF Proxy. Reduces MCP tool call token costs by 71%.
Install
codex plugin add gcf-proxy
What it does
Every MCP tool call returns JSON. This plugin wraps your MCP servers with GCF Proxy, which re-encodes those JSON responses as GCF before they reach the model.
The savings:
| Metric | Value |
|---|---|
| Token reduction vs JSON | 71% |
| Token reduction vs TOON | 25% |
| Session dedup (warm session) | up to 92% |
| Comprehension accuracy | 100% across 1,700+ LLM evaluations |
Skills
| Skill | Description |
|---|---|
/gcf-proxy:setup <server> | Wrap any MCP server with gcf-proxy |
/gcf-proxy:stats | Show token savings for the current session |
Hooks
- SessionStart: Clears stale stats from previous sessions
- Stop: Shows notification with calls rewritten, % saved, 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
- 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.
- Subsequent calls (up to 92%): Session deduplication detects repeated structure. Only deltas are transmitted.
- Zero code changes: The proxy wraps any MCP server. The server still outputs JSON; the proxy re-encodes before it reaches the model.
Cost example
A team running 1,000 queries/day with GPT-5.5 ($5/MTok input):
| Format | Monthly cost | Annual cost |
|---|---|---|
| JSON | $12,098 | $145,171 |
| GCF | $3,549 | $42,583 |
| Savings | $8,549/mo | $102,588/yr |
Try the cost calculator with your own numbers.
Links
License
MIT