BC Calculator MCP Server

A Model Context Protocol (MCP) server that provides numerical computation capabilities by integrating with the Unix bc (Basic Calculator) command-line tool. This server exposes arbitrary precision arithmetic operations, mathematical functions, and complex expressions through the MCP protocol.

Features

✨ Arbitrary Precision Arithmetic: Support for calculations with configurable decimal precision (0-100 digits)
🧮 Advanced Math Functions: Access to bc's math library including sqrt, sin, cos, arctan, natural log, exponential
🔄 Concurrent Processing: Process pool management for handling multiple calculations simultaneously
🛡️ Security First: Input validation and sanitization to prevent command injection
⚡ Performance Optimized: Process pooling for fast response times
🎯 MCP Compliant: Full MCP protocol implementation with tool discovery and JSON-RPC communication

Installation

Prerequisites

Node.js (v18 or higher)
TypeScript (v5.3 or higher)
bc calculator (standard on most Unix systems)

Verify bc is installed:

which bc bc --version

If not installed:

# Ubuntu/Debian sudo apt-get install bc # macOS brew install bc # Fedora/RHEL sudo dnf install bc

Setup

Navigate to MCP servers directory:

cd /home/travis/.local/share/Roo-Code/MCP

Bootstrap the project (if using create-server):

npx @modelcontextprotocol/create-server bc-calculator cd bc-calculator

Or manually create the project structure:

mkdir -p bc-calculator/src cd bc-calculator

Install dependencies:

npm install

Build the server:

npm run build

Configure MCP settings:

Add to ~/.config/Code/User/globalStorage/rooveterinaryinc.roo-cline/settings/mcp_settings.json:

{ "mcpServers": { "bc-calculator": { "command": "node", "args": ["/home/travis/.local/share/Roo-Code/MCP/bc-calculator/build/index.js"] } } }

Usage

Available Tools

1. `calculate`

Evaluate basic mathematical expressions with configurable precision.

Parameters:

expression (string, required): Mathematical expression to evaluate
precision (number, optional): Decimal places for the result (default: 20, range: 0-100)

Examples:

// Basic arithmetic calculate({ expression: "2 + 2" }) // → { result: "4", expression: "2 + 2", precision: 20 } // Division with precision calculate({ expression: "355/113", precision: 15 }) // → { result: "3.141592920353982", expression: "355/113", precision: 15 } // Powers and roots calculate({ expression: "2^10" }) // → { result: "1024", expression: "2^10", precision: 20 } calculate({ expression: "sqrt(2)", precision: 10 }) // → { result: "1.4142135623", expression: "sqrt(2)", precision: 10 }

2. `calculate_advanced`

Execute advanced BC scripts with variables, functions, and control flow.

Parameters:

script (string, required): Multi-line BC script
precision (number, optional): Decimal places for results (default: 20)

Examples:

// Variables calculate_advanced({ script: ` a = 5 b = 10 a * b + sqrt(a) `, precision: 5 }) // Computing pi calculate_advanced({ script: ` scale=15 pi = 4*a(1) pi ` }) // → { result: "3.141592653589793", ... } // Fibonacci sequence calculate_advanced({ script: ` a = 0 b = 1 for (i = 0; i < 10; i++) { c = a + b a = b b = c } b ` })

3. `set_precision`

Set the default precision for subsequent calculations.

Parameters:

precision (number, required): Number of decimal places (0-100)

Example:

set_precision({ precision: 50 }) // All subsequent calculations will use 50 decimal places

Mathematical Functions (with -l flag)

When using the math library, these functions are available:

Function	Description	Example
`sqrt(x)`	Square root	`sqrt(2)` → 1.41421...
`s(x)`	Sine (radians)	`s(3.14159/2)` → 1.0
`c(x)`	Cosine (radians)	`c(0)` → 1.0
`a(x)`	Arctangent (radians)	`a(1)` → 0.78539...
`l(x)`	Natural logarithm	`l(2.71828)` → 1.0
`e(x)`	Exponential (e^x)	`e(1)` → 2.71828...

Supported Operators

Arithmetic: +, -, *, /, ^ (power), % (modulo)
Comparison: <, >, <=, >=, ==, !=
Logical: &&, ||, !
Assignment: =
Increment/Decrement: ++, --

BC Language Features

Variables: a = 5; b = 10; a + b
Arrays: a[0] = 1; a[1] = 2
Conditionals: if (x > 0) { ... }
Loops: while (i < 10) { ... }, for (i=0; i<10; i++) { ... }
Functions: Define custom functions with define

Architecture

Process Pool

The server maintains a pool of 3 BC processes to handle concurrent requests:

┌─────────────────────────────────────┐ │ BC Calculator MCP Server │ ├─────────────────────────────────────┤ │ Process Pool Manager │ │ ┌─────────┐ ┌─────────┐ ┌─────────┐│ │ │ BC #1 │ │ BC #2 │ │ BC #3 ││ │ │ (ready) │ │ (busy) │ │ (ready) ││ │ └─────────┘ └─────────┘ └─────────┘│ ├─────────────────────────────────────┤ │ Request Queue │ │ • Validation │ │ • Sanitization │ │ • Timeout Management │ └─────────────────────────────────────┘

Security Features

Input Validation
- Character whitelist enforcement
- Maximum expression length (10KB)
- Dangerous pattern detection
Command Injection Prevention
- No shell execution (spawn with shell: false)
- Input sanitization before BC
- Blocked patterns: system(), exec(), backticks, file redirects
Resource Protection
- 30-second timeout per calculation
- Process pool size limit (3 processes)
- Automatic process recovery on failures

Error Handling

The server provides detailed error messages for common issues:

Validation Errors

{ "isError": true, "content": [{ "type": "text", "text": "Validation error: Expression contains invalid characters" }] }

BC Runtime Errors

{ "isError": true, "content": [{ "type": "text", "text": "BC error: divide by zero" }] }

Timeout Errors

{ "isError": true, "content": [{ "type": "text", "text": "Calculation timeout after 30000ms" }] }

Configuration

Default Settings

Process Pool Size: 3 concurrent BC processes
Default Precision: 20 decimal places
Calculation Timeout: 30 seconds
Max Expression Length: 10,000 characters

Environment Variables

None required - bc is a standard system utility.

Optional: Custom Pool Size

Edit src/index.ts to adjust pool configuration:

const pool = new BCProcessPool({ poolSize: 5, // Increase for more concurrency defaultPrecision: 20, defaultTimeout: 60000 // Increase for longer calculations });

Development

Project Structure

bc-calculator/ ├── package.json ├── tsconfig.json ├── README.md ├── src/ │ ├── index.ts # MCP server entry point │ ├── types.ts # TypeScript definitions │ ├── bc-process.ts # BC process wrapper │ ├── bc-process-pool.ts # Process pool manager │ ├── input-validator.ts # Security validation │ └── request-queue.ts # Request management └── build/ # Compiled JavaScript └── index.js

Build Commands

# Build once npm run build # Watch mode (rebuild on changes) npm run watch # Clean build rm -rf build && npm run build

Testing

# Manual testing via MCP client # Use the Roo-Code interface to invoke tools # Example test cases: # 1. Basic: calculate("2+2") # 2. Precision: calculate("22/7", precision=10) # 3. Math: calculate("sqrt(2)*sqrt(2)", precision=15) # 4. Error: calculate("2/0") # 5. Advanced: calculate_advanced("a=5; b=10; a+b")

Troubleshooting

BC Not Found

Error: spawn bc ENOENT

Solution: Install bc calculator

sudo apt-get install bc # Ubuntu/Debian brew install bc # macOS

Permission Denied

Error: Cannot execute build/index.js

Solution:

chmod +x build/index.js

Module Import Errors

Error: Cannot find module

Solution: Ensure "type": "module" is in package.json

Timeout on Complex Calculations

Symptom: Long-running calculations fail

Solution: Increase timeout in tool parameters or pool config

Process Pool Exhausted

Symptom: Delayed responses under heavy load

Solution: Increase poolSize in BCProcessPool configuration

Performance

Benchmarks

Simple arithmetic: <10ms
Math functions: <50ms
Complex scripts: <200ms
Concurrent requests: 3 parallel calculations

Optimization Tips

Reuse connections: The process pool automatically optimizes this
Batch operations: Use calculate_advanced for multiple related calculations
Adjust precision: Lower precision = faster calculations
Increase pool: For heavy concurrent use, increase pool size

Contributing

Contributions welcome! Please:

Maintain TypeScript strict mode compliance
Add tests for new features
Update documentation
Follow existing code style
Ensure security validations remain intact

License

MIT License - See LICENSE file for details

Acknowledgments

Built on the Model Context Protocol SDK
Uses the standard GNU bc calculator
Inspired by the need for arbitrary precision arithmetic in AI applications

Support

For issues, questions, or feature requests:

Check the troubleshooting section
Review the implementation guide (IMPLEMENTATION_GUIDE.md)
Examine the architecture documentation (ARCHITECTURE.md)

Version History

1.0.0 (Initial Release)

Basic calculation support
Advanced scripting support
Process pool management
Security validation
MCP protocol compliance

BC Calculator MCP Server

Features

Installation

Prerequisites

Setup

Usage

Available Tools

1. calculate

2. calculate_advanced

3. set_precision

Mathematical Functions (with -l flag)

Supported Operators

BC Language Features

Architecture

Process Pool

Security Features

Error Handling

Validation Errors

BC Runtime Errors

Timeout Errors

Configuration

Default Settings

Environment Variables

Optional: Custom Pool Size

Development

Project Structure

Build Commands

Testing

Troubleshooting

BC Not Found

Permission Denied

Module Import Errors

Timeout on Complex Calculations

Process Pool Exhausted

Performance

Benchmarks

Optimization Tips

Contributing

License

Acknowledgments

Support

Version History

1.0.0 (Initial Release)

Related Resources

New MCP Servers

MCP directory API

1. `calculate`

2. `calculate_advanced`

3. `set_precision`