gcf-claude-plugin

Claude Code plugin for GCF Proxy. Reduces MCP tool call token costs by 71%.

Install

/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, 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:

{
  "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 with your own numbers.

Requirements

• Node.js 18+
• Claude Code with plugin support

Links

• GCF Spec
• GCF Proxy
• Benchmarks (1,700+ LLM evaluations, 100% comprehension accuracy)
• Cost Calculator

License

MIT