Simple Skill

Simple Skill

A minimal example demonstrating how easy it is to create skills with Skill Engine. This skill showcases the basic patterns for defining tools, handling parameters, and returning results - perfect for learning or as a template for new skills.

Overview

This skill requires no build steps - just write JavaScript and run! The runtime automatically compiles to WASM on first run and caches the result for fast subsequent executions.

When to Use This Skill

Use this skill to:

• Learn the basics of Skill Engine development
• Test skill execution and parameter handling
• Understand the skill.js file structure
• Use as a template for creating new skills

Use this skill as a reference when:

• Starting a new skill from scratch
• Understanding parameter types and validation
• Learning error handling patterns
• Setting up tool metadata

Features

• No build steps required - Just write JavaScript and run
• Auto-compilation - Runtime compiles to WASM on first run (~2-3 seconds) and caches
• Fast execution - Subsequent runs use cached WASM (<100ms startup)
• Auto-recompile - Modifications to skill.js trigger automatic recompilation
• Simple API - Export functions matching the skill interface
• Type-safe - Tool definitions provide schema for arguments

Tools

hello

Greet someone with a friendly message.

Example:

# Basic greeting
skill run simple-skill hello name=World
# Output: Hello, World! 👋

# Custom greeting
skill run simple-skill hello name=Alice greeting="Hi"
# Output: Hi, Alice! 👋

# Direct path execution
skill run ./examples/wasm-skills/simple-skill hello name=Bob

echo

Echo back the provided message, optionally repeating it multiple times.

Example:

# Simple echo
skill run simple-skill echo message="Hello World"
# Output: Hello World

# Repeat 3 times
skill run simple-skill echo message="Testing" repeat=3
# Output:
# Testing
# Testing
# Testing

# Echo with special characters
skill run simple-skill echo message="Skills are great!" repeat=2

calculate

Perform basic arithmetic operations on two numbers.

Example:

# Addition
skill run simple-skill calculate operation=add a=10 b=5
# Output: 10 add 5 = 15

# Subtraction
skill run simple-skill calculate operation=subtract a=20 b=8
# Output: 20 subtract 8 = 12

# Multiplication
skill run simple-skill calculate operation=multiply a=7 b=6
# Output: 7 multiply 6 = 42

# Division
skill run simple-skill calculate operation=divide a=100 b=4
# Output: 100 divide 4 = 25

# Decimals work too
skill run simple-skill calculate operation=divide a=22 b=7
# Output: 22 divide 7 = 3.142857142857143

How It Works

First Run (Compilation)

1. Runtime detects skill.js needs compilation
2. Compiles JavaScript → WASM (takes ~2-3 seconds)
3. Stores compiled WASM in ~/.skill-engine/local-cache/
4. Executes the tool

Subsequent Runs (Cached)

1. Runtime finds cached WASM
2. Loads from cache (<100ms startup)
3. Executes immediately

After Modifications

1. Runtime detects skill.js changed (via hash)
2. Automatically recompiles to WASM
3. Updates cache
4. Executes with new code

Skill Structure

This skill demonstrates the minimal required structure:

// 1. Metadata - Basic information about your skill
export function getMetadata() {
  return {
    name: "simple-skill",
    version: "1.0.0",
    description: "A simple example skill",
    author: "Skill Engine Team"
  };
}

// 2. Tool Definitions - Declare available tools and their parameters
export function getTools() {
  return [
    {
      name: "hello",
      description: "Greet someone",
      parameters: [
        {
          name: "name",
          paramType: "string",        // Type: string, number, boolean
          description: "Name to greet",
          required: true,              // Is this parameter required?
          defaultValue: "World"        // Optional default value
        }
      ]
    }
  ];
}

// 3. Tool Execution - Handle tool invocations
export async function executeTool(toolName, argsJson) {
  const args = JSON.parse(argsJson);

  if (toolName === "hello") {
    return {
      success: true,
      output: `Hello, ${args.name}!\n`,
      errorMessage: null
    };
  }

  return {
    success: false,
    output: "",
    errorMessage: `Unknown tool: ${toolName}`
  };
}

// 4. Config Validation (Optional) - Validate configuration
export async function validateConfig() {
  return { ok: null };
}

Parameter Types Reference

When defining tools in getTools(), use these parameter types:

Parameter Properties

{
  name: "param_name",           // Parameter name (use snake_case)
  paramType: "string",          // Type: string, number, boolean
  description: "What it does",  // Clear description for users
  required: true,               // true = required, false = optional
  defaultValue: "default"       // Optional: default if not provided
}

Development Workflow

1. Create Your Skill

# Create directory
mkdir my-skill
cd my-skill

# Create skill.js (copy from examples/wasm-skills/simple-skill/skill.js)
cat > skill.js << 'EOF'
export function getMetadata() {
  return {
    name: "my-skill",
    version: "1.0.0",
    description: "My first skill"
  };
}
// ... add getTools() and executeTool() ...
EOF

2. Test Locally

# Run directly without installing
skill run ./my-skill tool-name param1=value1

# Check tool list
skill info ./my-skill

# View parameter help
skill run ./my-skill tool-name --help

3. Iterate Quickly

# 1. Edit skill.js
vim skill.js

# 2. Run immediately (auto-recompiles)
skill run ./my-skill tool-name

# No build steps, no npm install, no package.json needed!

4. Install (Optional)

# Once ready, install globally
skill install ./my-skill

# Now run from anywhere
skill run my-skill tool-name

Using Configuration (Advanced)

If your skill needs configuration (API keys, URLs, etc.):

1. Create skill.config.toml

[config]
api_key = "your-key-here"
api_url = "https://api.example.com"
timeout = 30

2. Access via Environment Variables

Configuration is automatically exposed as environment variables with SKILL_ prefix:

export async function executeTool(toolName, argsJson) {
  const apiKey = process.env.SKILL_API_KEY;
  const apiUrl = process.env.SKILL_API_URL;
  const timeout = parseInt(process.env.SKILL_TIMEOUT || "30");

  // Use configuration in your tool logic
}

3. Validate Configuration

export async function validateConfig() {
  const apiKey = process.env.SKILL_API_KEY;

  if (!apiKey) {
    return {
      ok: null,
      error: "SKILL_API_KEY is required"
    };
  }

  return { ok: null };
}

TypeScript Support

You can write skills in TypeScript - just change the extension:

# Rename to .ts
mv skill.js skill.ts

# Runtime automatically compiles TypeScript → JavaScript → WASM
skill run ./my-skill tool-name

Error Handling Best Practices

Return Proper Error Messages

// Bad - unclear error
return { success: false, output: "", errorMessage: "Error" };

// Good - specific error
return {
  success: false,
  output: "",
  errorMessage: "Invalid operation: 'foo'. Use: add, subtract, multiply, or divide"
};

Validate Input Early

function handleCalculate(args) {
  // Validate first
  if (isNaN(parseFloat(args.a)) || isNaN(parseFloat(args.b))) {
    return {
      success: false,
      output: "",
      errorMessage: "Both 'a' and 'b' must be valid numbers"
    };
  }

  // Then process
  const result = parseFloat(args.a) + parseFloat(args.b);
  return { success: true, output: `${result}\n`, errorMessage: null };
}

Handle Edge Cases

function handleDivide(args) {
  const a = parseFloat(args.a);
  const b = parseFloat(args.b);

  // Check for division by zero
  if (b === 0) {
    return {
      success: false,
      output: "",
      errorMessage: "Cannot divide by zero"
    };
  }

  return { success: true, output: `${a / b}\n`, errorMessage: null };
}

Best Practices

1. Keep it simple - Skills should be focused and do one thing well
2. Document parameters - Use clear, descriptive parameter descriptions
3. Validate input - Check required parameters and types early
4. Return meaningful errors - Help users understand what went wrong
5. Use descriptive names - Tool and parameter names should be self-explanatory
6. Provide examples - Show real usage examples in SKILL.md
7. Test edge cases - Handle invalid input gracefully
8. Follow conventions - Use snake_case for parameters, lowercase for tool names

Testing Your Skill

# List available tools
skill info simple-skill

# Test each tool
skill run simple-skill hello name=Test
skill run simple-skill echo message="Testing 123"
skill run simple-skill calculate operation=add a=2 b=2

# Check parameter validation
skill run simple-skill hello                    # Missing required param
skill run simple-skill calculate operation=add  # Missing required params

# Test edge cases
skill run simple-skill calculate operation=divide a=10 b=0  # Division by zero
skill run simple-skill echo message="Test" repeat=-1         # Negative repeat

Next Steps

After mastering this simple skill:

1. Study More Examples:

   • github-skill - HTTP API integration
   • slack-skill - OAuth authentication
   • kubernetes-skill - Native tool execution

2. Learn the SDK:

   • Type-safe parameter validation
   • HTTP client utilities
   • Error handling helpers
   • Authentication patterns

3. Build Real Skills:

   • Integrate with APIs you use
   • Automate your workflows
   • Share with the community

Resources

• Skill Engine Documentation
• SDK Reference
• Example Skills
• Community Skills

License

MIT - Use as a template for your own skills!

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