MCP proxy that re-encodes JSON tool responses as GCF. Drop-in, zero changes to your server.
84% fewer tokens. 100% comprehension accuracy. One line change in your MCP config.
go install github.com/blackwell-systems/gcf-proxy@latest{
"mcpServers": {
"memory": {
"command": "gcf-proxy",
"args": ["memory-mcp-server-go"]
}
}
}That's it. Your server keeps outputting JSON. The LLM receives GCF. Nothing else changes.
{"tool":"context_for_task","symbols":[{"qualified_name":"pkg.Auth","kind":"function","score":0.78,...},...]}GCF tool=context_for_task budget=5000 tokens=1900 symbols=50
## targets
@0 fn pkg.Auth 0.78 lsp_resolved
...
## edges
@0<@1 calls
- Spawns your MCP server as a subprocess
- Proxies stdin/stdout between client and server
- Intercepts JSON-RPC responses containing tool results
- Detects JSON payloads with
tool+symbolsfields - Re-encodes them as GCF
- Passes everything else through unchanged
Non-convertible responses (plain text, HTML, errors) pass through untouched.
Sometimes you can't. The server is a third-party binary, or it's maintained by another team, or you just don't want to add a dependency. gcf-proxy gives you the token savings without touching server code.
If you control the server, use the GCF libraries directly for better control over session deduplication and delta encoding.
MIT