SymDex: Open-Source MCP Code Indexer Reduces AI Agent Token Usage

What SymDex Does

SymDex addresses a specific problem with current AI coding agents: when asked to find a function, they typically read the entire file containing that function, burning through context window tokens before doing any real work. The developer built SymDex because every AI agent they used was reading entire files just to find one function.

The Token Math

According to the source material, a 300-line file contains approximately 10,500 characters. With BPE tokenizers (used by major LLMs) processing roughly 3-4 characters per token, that's about 3,000 tokens for the code, plus indentation whitespace and response framing, totaling approximately 3,400 tokens to look up one function. A real debugging session might touch 8-10 files, consuming most of the context window before any fixes are made.

How It Works

SymDex pre-indexes your codebase once. After indexing, your agent knows exactly where every function and class is without reading full files. The same 300-line file that costs ~3,400 tokens to read returns results in ~100 tokens with SymDex.

Additional features include:

• Semantic search locally (find functions by what they do, not just name)
• Call graph tracking so your agent knows what breaks before touching anything

Getting Started

Installation and basic usage:

pip install symdex
symdex index ./your-project --name myproject
symdex search "validate email"

Compatibility and Licensing

SymDex works with Claude, Codex, Gemini CLI, Cursor, Windsurf, and any MCP-compatible agent. It also has a standalone CLI. The tool is free, MIT licensed, and runs entirely on your machine. It supports 12 programming languages.