MCP Integration

a-calc ships a built-in MCP server so AI assistants can use a-calc for precise calculations and formatting.

Quick Start

1. Install

npm install a-calc

2. Configure Your AI Tool

Add to your config file:

Claude Desktop

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
• Windows: %APPDATA%\Claude\claude_desktop_config.json

Cline / Trae / other MCP clients — add in the corresponding settings

Config:

{
  "mcpServers": {
    "a-calc": {
      "command": "npx",
      "args": ["a-calc-mcp"]
    }
  }
}

💡 Note: Claude Desktop defaults to the project root directory and will automatically use the locally installed a-calc if present. Otherwise npx downloads the latest version.

Troubleshooting:

If the MCP server fails to start, try in order:

1. Add cwd config (required by some editors like Trae):

   {
     "mcpServers": {
       "a-calc": {
         "command": "npx",
         "args": ["a-calc-mcp"],
         "cwd": "${workspaceFolder}"
       }
     }
   }

2. Global install:

   npm install -g a-calc

   Then use:

   {
     "mcpServers": {
       "a-calc": {
         "command": "a-calc-mcp"
       }
     }
   }

3. Windows note: If you see Windows requires 'cmd /c' wrapper, change npx to cmd /c npx

3. Restart Your AI Tool

Restart after configuration and you're ready to go.

Available Tools

Tool	Purpose	Example
calc	Expression evaluation	calc("0.1 + 0.2") → "0.3"
fmt	Number formatting	fmt(1234567, ",") → "1,234,567"
calc_sum	Batch summation	calc_sum("price * qty", [...])
basic_calc	Basic arithmetic	basic_calc("add", [0.1, 0.2])
chain_calc	Chain calculation	cadd(100).mul(0.8)()

Usage Examples

User: Calculate 0.1 + 0.2
AI: [calls calc] → 0.3

User: Format 1234567.89 with thousands separator and 2 decimal places
AI: [calls fmt] → 1,234,567.89

User: Calculate order total (Item A: 99.9×2, Item B: 49.9×3)
AI: [calls calc_sum] → 349.50

Troubleshooting

Issue	Solution
Server won't start	1. Add cwd: "${workspaceFolder}" config 2. Try global install npm install -g a-calc 3. Ensure Node.js ≥ 18
Tool call fails	Check expression syntax and parameter format
Windows error	Change npx to cmd /c npx

Related Links

• MCP Official Docs
• a-calc API Reference