gcf-proxy
Bidirectional MCP proxy that translates between GCF and JSON. Drop-in, zero code changes to your server or client.
50-92% fewer tokens. 100% comprehension on every frontier model and 3 providers. 2,400+ LLM evaluations. Zero training.
Docs: gcformat.com · Proxy Guide · Playground · GCF vs TOON
Install
pip install gcf-proxy
Setup (one line change)
Before:
{"mcpServers": {"yours": {"command": "your-mcp-server"}}}
After:
{"mcpServers": {"yours": {"command": "gcf-proxy", "args": ["your-mcp-server"]}}}
Works with Claude Code, Claude Desktop, VS Code, Cursor, and any MCP client.
What it does
Translates in both directions:
Responses: Your Server (JSON) -> gcf-proxy encodes -> LLM reads GCF (50-92% savings)
Requests: LLM writes GCF -> gcf-proxy decodes -> Your Server (JSON) (63% output savings)
- Responses: JSON tool results from the server are encoded as GCF
- Requests: GCF strings in tool call arguments are decoded to JSON (4-byte prefix check, zero overhead)
- Non-convertible content passes through unchanged in both directions
- Neither the server nor the client needs to know about GCF
--no-flattenuses expanded encoding for nested objects (open-weight models currently comprehend this form better; GCF still outperforms JSON either way)
Savings
JSON 2,506 bytes ~626 tokens
GCF 916 bytes ~229 tokens (63% fewer)
With session dedup (92.7% by 5th call) and delta encoding (81.2%), use the GCF libraries directly.
Benchmarks
| Eval | GCF | TOON | JSON |
|---|---|---|---|
| General comprehension | 100% | 100% | 100% |
| Adversarial code graphs (500 symbols) | 91.2% | 68.8% | 54.1% |
| Token efficiency (16 datasets) | 15/16 wins | 1/16 | baseline |
Also available on
- npm:
npm install -g @blackwell-systems/gcf-proxy - Go:
go install github.com/blackwell-systems/gcf-proxy@latest
Links
1 maintainer
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