Legacy Code Interpreter Skill

Deep analysis and interpretation of legacy code to understand undocumented behavior, extract business logic, and characterize system functionality.

Purpose

Enable legacy code understanding for:

• Business logic extraction
• Undocumented feature discovery
• Behavior characterization
• Migration planning
• Knowledge preservation

Capabilities

1. Business Logic Extraction

• Parse conditional logic
• Extract calculation formulas
• Identify validation rules
• Document decision trees

2. Undocumented Feature Discovery

• Find hidden functionality
• Identify feature flags
• Discover Easter eggs
• Map admin features

3. Control Flow Analysis

• Trace execution paths
• Map state machines
• Identify loops and recursion
• Document entry points

4. Data Flow Tracking

• Trace data transformations
• Map input to output
• Identify side effects
• Document state changes

5. Side Effect Identification

• Find external calls
• Identify I/O operations
• Map database operations
• Document messaging

6. Behavior Characterization

• Create behavior summaries
• Generate pseudo-code
• Document edge cases
• Map error handling

Tool Integrations

Tool	Purpose	Integration Method
Understand (SciTools)	Deep analysis	CLI / API
Lattix	Architecture analysis	CLI
CodeScene	Behavioral analysis	API
Sourcetrail	Code exploration	CLI
ast-grep	Pattern matching	MCP / CLI

Output Schema

{
  "analysisId": "string",
  "timestamp": "ISO8601",
  "interpretation": {
    "businessLogic": [
      {
        "name": "string",
        "location": "string",
        "description": "string",
        "pseudoCode": "string",
        "inputs": [],
        "outputs": [],
        "sideEffects": []
      }
    ],
    "controlFlow": {
      "entryPoints": [],
      "stateMachines": [],
      "criticalPaths": []
    },
    "dataFlow": {
      "transformations": [],
      "stateChanges": []
    },
    "undocumented": []
  }
}

Integration with Migration Processes

• legacy-codebase-assessment: Primary interpretation tool
• migration-planning-roadmap: Knowledge source

Related Skills

• static-code-analyzer: Structural analysis
• knowledge-extractor: Documentation mining

Related Agents

• legacy-system-archaeologist: Uses for excavation