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LucasBiason
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legacy-specifier

Extract API contracts, data schemas, and behavioral rules from legacy codebases.

Updated Aug 27, 2026
Search Tags:#documentation#codebase#specification#contracts#tests#apis#reverse-engineer
One-click install
npx skills add https://github.com/LucasBiason/engineering-knowledge-base --skill legacy-specifier
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: legacy-specifier
Source: https://github.com/LucasBiason/engineering-knowledge-base/tree/main/.claude/skills/workflow/legacy-specifier
Command: npx skills add https://github.com/LucasBiason/engineering-knowledge-base --skill legacy-specifier

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

This skill helps teams reverse-engineer specifications from legacy systems where documentation is missing, turning opaque code into clear contracts.

Core Features & Use Cases

  • Extracts API contracts, data schemas, and behavioral rules from code, tests, and UI flows.
  • Produces a structured set of spec files (system context, API contracts, feature specs) to guide refactoring and maintenance.
  • Handles evidence-driven inference and explicitly marks unknowns when evidence is insufficient.

Quick Start

Run the legacy-specifier on a repository to generate structured spec artifacts from existing code.

Frequently Asked Questions about legacy-specifier

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I extract specifications from a legacy codebase with missing documentation?▼

To extract specifications from a legacy codebase, analyze repository code, API schemas, test suites, and UI flows to generate structured contract-oriented spec artifacts and open questions when evidence is insufficient.

What is reverse-engineering API contracts from existing code?▼

Reverse-engineering API contracts from existing code involves analyzing legacy systems, API schemas, and tests to reveal behavior, data schemas, and business rules, producing structured spec files under the spec/ directory.

Can I generate feature specifications from test suites and UI flows?▼

Yes, you can generate feature specifications from test suites and UI flows by applying evidence-driven inference to extract behavioral rules and system context, explicitly marking unknowns when evidence is insufficient.

Does this approach work for reverse-engineering business rules from legacy systems?▼

Yes, this approach works for reverse-engineering business rules from legacy systems by examining existing repository code and UI flows to reveal behavior and produce contract-oriented artifacts to guide refactoring.

What is the best way to document opaque legacy code for refactoring?▼

The best way to document opaque legacy code for refactoring is to extract API contracts, data schemas, and behavioral rules, generating a structured set of spec files like system context and feature specs.

How are unknown behaviors handled when extracting specifications from code?▼

When extracting specifications from code, unknown behaviors are handled through evidence-driven inference that explicitly marks open questions in the generated spec artifacts when evidence is insufficient to determine a contract.

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