Content
# gcf-claude-plugin
Claude Code plugin for [GCF Proxy](https://github.com/blackwell-systems/gcf-proxy). Reduces MCP tool call token costs by 71%.
## Install
```bash
/plugin install blackwell-systems/gcf-claude-plugin
```
## What it does
Every MCP tool call returns JSON. This plugin wraps your MCP servers with [GCF Proxy](https://github.com/blackwell-systems/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 |
Same data. Fewer tokens. Lower cost on every tool call, every session.
## Skills
| Skill | Description |
|-------|-------------|
| `/gcf-proxy:setup <server>` | Wrap any existing MCP server with gcf-proxy. Preserves original config for easy revert. |
| `/gcf-proxy:stats` | Show token savings for the current session. |
## Quick start
After installing, wrap any MCP server:
```
/gcf-proxy:setup github
```
This modifies your MCP config to route the `github` 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 (no primer needed).
2. **Subsequent calls (up to 92%):** GCF session deduplication detects repeated structure across tool calls in the same session. Only deltas are transmitted. By the 5th call in a session, token usage drops to 8% of the original JSON cost.
3. **Zero code changes:** gcf-proxy wraps any MCP server. The server still outputs JSON; the proxy re-encodes it before it reaches the model.
## Manual setup
If you prefer to configure manually, edit your `.mcp.json`:
```json
{
"mcpServers": {
"my-server": {
"command": "npx",
"args": ["-y", "@blackwell-systems/gcf-proxy@latest", "npx", "-y", "your-mcp-server"]
}
}
}
```
## Cost example
A team running 1,000 queries/day with Claude Sonnet 4.6 ($3/MTok input):
| Format | Monthly cost | Annual cost |
|--------|-------------|-------------|
| JSON | $7,259 | $87,103 |
| GCF | $2,129 | $25,543 |
| **Savings** | **$5,130/mo** | **$61,560/yr** |
[Try the cost calculator](https://gcformat.com/calculator) with your own numbers.
## Requirements
- Node.js 18+
- Claude Code with plugin support
## Links
- [GCF Spec](https://gcformat.com)
- [GCF Proxy](https://github.com/blackwell-systems/gcf-proxy)
- [Benchmarks](https://gcformat.com/guide/benchmarks.html) (1,700+ LLM evaluations, 100% comprehension accuracy)
- [Cost Calculator](https://gcformat.com/calculator)
## License
MIT
