MCPack

MCP Response Compression Proxy — Like RTK but for MCP servers.

Reduces LLM token consumption 60-90% by compressing MCP tool responses before they reach your AI agent.

How it works

MCPack sits between your LLM client (Claude Code, Cursor, etc.) and any MCP server as a transparent proxy:

LLM Client  ←→  MCPack Proxy  ←→  MCP Server
                    ↓
            Strips verbose fields
            Truncates long arrays
            Compacts JSON output

Install

npm install -g mcpack

Quick Start

Wrap any MCP server with MCPack:

# Before (raw MCP responses, high token usage):
planning-game-mcp

# After (compressed responses, 60-90% fewer tokens):
mcpack -- planning-game-mcp

Claude Code Integration

In ~/.claude.json:

{
  "mcpServers": {
    "planning-game": {
      "command": "mcpack",
      "args": ["--preset", "planning", "--", "planning-game-mcp"],
      "env": {
        "GOOGLE_APPLICATION_CREDENTIALS": "/path/to/key.json"
      }
    }
  }
}

Presets

| Preset | Use case | Compression | |--------|----------|-------------| | minimal | Any MCP — compact JSON only | ~30-40% | | planning | Project management (tasks, sprints, cards) | ~70-85% | | code | Code tools (diffs, patches, reviews) | ~60-75% | | data | Database/data queries | ~50-65% | | aggressive | Maximum savings for long sessions | ~80-90% |

mcpack --preset planning -- my-mcp-server
mcpack --preset aggressive -- my-mcp-server

Custom Config

Create mcpack.json:

{
  "stripFromListItems": ["description", "body", "content"],
  "stripAlways": ["changelog", "history"],
  "maxArrayItems": 15,
  "maxStringLength": 200,
  "neverTruncateFields": ["id", "url", "email"],
  "compactJson": true,
  "transformers": {}
}

mcpack --config ./mcpack.json -- my-mcp-server

What it compresses

| Strategy | Example | Savings | |----------|---------|---------| | Field stripping | Remove description, acceptanceCriteria from list items | 50-70% per item | | Array truncation | 100 items → first 20 + count | 80% | | Compact JSON | No indentation ({a:1} vs {\n a: 1\n}) | 30-40% | | String truncation | 2000-char description → 300 chars | 85% |

Token Savings Example

A typical 30-minute Claude Code session managing 50 tasks:

| Operation | Without MCPack | With MCPack | Savings | |-----------|----------------|-------------|---------| | list_cards (50 tasks) | ~25,000 tokens | ~4,000 tokens | 84% | | update_card × 30 | ~60,000 tokens | ~9,000 tokens | 85% | | get_card × 10 | ~30,000 tokens | ~12,000 tokens | 60% | | Session total | ~115,000 tokens | ~25,000 tokens | 78% |

Development

git clone https://github.com/manufosela/mcpack
cd mcpack
npm install
npm test

License

MIT