OneTool MCP

The Problem

Each MCP server consumes 3K-30K tokens per request. Connect 5 servers and you've burned 55K tokens before the conversation starts. Connect 10+ and you're at 100K tokens.

The math is brutal: Claude Opus 4.5 at $5/M input tokens, 20 days × 10 conversations × 10 messages × 3K tokens = $30/month per MCP server - even if you never use the tools.

And then there's context rot - your AI literally gets dumber as you add more tools (Chroma Research, 2025).

The Solution

OneTool is one MCP server that exposes tools as a Python API. Instead of reading tool definitions, your agent writes code:

>>> brave.search(query="react docs 2026")

Configure one MCP server. Use unlimited tools.

"Agents scale better by writing code to call tools instead. This reduces the token usage from 150,000 tokens to 2,000 tokens...a cost saving of 98.7%"

— Anthropic Engineering

96% fewer tokens. 30× lower cost. No context rot.

📖 Read the full story

Install

Requires uv:

uv tool install 'onetool-mcp[all]'   # everything
onetool init --config ~/.onetool

Add to Claude Code:

claude mcp add onetool -- onetool --config ~/.onetool/onetool.yaml --secrets ~/.onetool/secrets.yaml

Or manually add to ~/.claude/mcp.json:

{
  "mcpServers": {
    "onetool": {
      "command": "onetool",
      "args": ["--config", "/Users/yourname/.onetool/onetool.yaml", "--secrets", "/Users/yourname/.onetool/secrets.yaml"]
    }
  }
}

That's it. All 100+ tools work out of the box.

Verify: onetool init validate --config ~/.onetool/onetool.yaml

📖 Full installation guide

Use from the CLI

Works as an MCP server and as a direct CLI — no MCP client needed. Useful for agent harnesses, scripts, and automation:

# Start a persistent execution host (keeps tool state across calls)
onetool direct start --config ~/.onetool/onetool.yaml

# Run any tool — JSON output, pipeable to jq
onetool direct run "ot.packs()" --format json | jq '.[0].name'
onetool direct run "brave.search(query='latest AI news')" --format raw

📖 Direct usage guide

Features

Tools

27+ packs, 230+ tools ready to use:

📖 Complete tools reference — full summary table with all 230+ tools

MCP Server Proxy

Wrap any existing MCP server and call it explicitly - simple yaml config without the tool tax:

# .onetool/onetool.yaml
servers:
  chrome_devtools:
    type: stdio
    command: npx
    args: ["-y", "@anthropic-ai/chrome-devtools-mcp@latest"]
  github:
    type: stdio
    command: npx
    args: ["-y", "@anthropic-ai/github-mcp-server@latest"]

>>> mcp.call(server="github", tool="get_file_contents", arguments={"path": "README.md"})

📖 Configuration guide

Extending

Drop a Python file, get a pack. No registration, no config:

# .onetool/tools/wiki.py
pack = "wiki"

def summary(*, title: str) -> str:
    """Get Wikipedia article summary."""
    import httpx
    url = f"https://en.wikipedia.org/api/rest_v1/page/summary/{title}"
    return httpx.get(url).json().get("extract", "Not found")

>>> wiki.summary(title="Python_(programming_language)")

📖 Creating tools guide

Documentation

• Quickstart - 30 seconds to first tool call
• Installation - All platforms
• Configuration - YAML schema
• Tools Reference - All 100+ tools
• Security - Security layers
• Extending - Build your own
• Dev Docs - Internal developer documentation
• Specifications - OpenSpec specifications index

References

• Code Execution with MCP - Anthropic Engineering
• Context Rot - Chroma Research

Telemetry

OneTool sends anonymous startup pings (event type, version, OS). No personal data. Opt out: export DO_NOT_TRACK=1 or set telemetry.enabled: false in onetool.yaml. Details

Issues

Check for existing issues first:

• Browse the tracker: github.com/beycom/onetool-mcp/issues
• Search with GitHub syntax: is:issue repo:beycom/onetool-mcp <keyword>

Raise a new issue: github.com/beycom/onetool-mcp/issues/new

Support

If you find OneTool useful:

License

GPLv3