What problem does it solve? When testing a live API without documentation, testers often jump straight to payloads without understanding the endpoint's structure. This Skill provides a disciplined methodology to reverse-engineer an API's schema, state machine, authentication boundaries, and hidden routes from observed request/response behavior before attempting exploitation. ## Core Features & Use Cases - Parameter Semantics Matrix: Builds a baseline-vs-probe comparison matrix where each probe changes only one variable (parameter, encoding, or state) to infer types, required fields, defaults, and constraints. - Adaptive Decision Tree: Guides the tester to deepen schema inference, pivot on rate limits, backtrack on catch-all routes, or wait for new signals based on response classification. - Structured Handoff: Routes discovered artifacts (object IDs, writable fields, tokens, callbacks, templates) to specialized follow-up skills such as IDOR, SQLi, JWT, SSRF, or SSTI analysis. - Use Case: During an authorized assessment, you capture a /api/v2/user endpoint returning different schemas for detail=true vs full=true. The Skill walks you through isolating the route selector, mapping the state machine, and handing the discovered object ID to IDOR testing. ## Quick Start Ask the agent to reverse-engineer the schema and state machine of a captured API endpoint using its saved request and response samples.
