gcf-proxy 0.1.0

MCP proxy that re-encodes JSON tool responses as GCF. Zero code changes.

gcf-proxy

MCP proxy that re-encodes JSON tool responses as GCF — the most token-efficient wire format for LLMs. Drop-in, zero code changes. A TOON/JSON alternative that saves 63-79% of tokens.

79% fewer tokens than JSON. 34% fewer than TOON. 100% LLM comprehension at scale.

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"]}}}

Your server keeps outputting JSON. The LLM receives GCF. Nothing else changes.

Works with Claude Code, Claude Desktop, VS Code, Cursor, and any MCP client.

What it does

LLM  ←──  GCF  ←──  gcf-proxy  ←──  JSON  ←──  Your Server

1. Spawns your MCP server as a subprocess
2. Proxies stdin/stdout between client and server
3. Detects JSON payloads in tool responses
4. Re-encodes as GCF (graph profile for code intelligence, tabular profile for everything else)
5. Non-convertible responses (text, HTML, errors) pass through unchanged

Savings

Tested on a real MCP tool response (10 symbols, 8 edges):

JSON   2,506 bytes  ~626 tokens
GCF      916 bytes  ~229 tokens

Savings: 63% fewer tokens

On a real agent-lsp blast_radius response (7 symbols, 47 callers):

JSON   6,515 bytes  ~1,628 tokens
GCF    4,866 bytes  ~1,216 tokens

Savings: 25% fewer tokens (generic encoding, no graph profile)

When to use

• You can't modify the server (third-party binary, another team's code)
• You want to test GCF savings without writing any code
• You want zero-effort adoption on any existing MCP server

For session deduplication (92.7% savings) and delta encoding (81.2% savings), use the GCF libraries directly.

Also available on

• npm: npm install -g @blackwell-systems/gcf-proxy
• Go: go install github.com/blackwell-systems/gcf-proxy@latest

Links

• Full Setup Guide
• GCF Specification
• GCF vs TOON
• Playground
• GitHub