okhp3-custom-gpt-builderlisted

# okhp3-custom-gpt-builder **OverKill Hill P³** · [overkillhill.com](https://overkillhill.com) · [github.com/OKHP3](https://github.com/OKHP3) A production-grade methodology for designing, building, testing, and maintaining OpenAI Custom GPTs. Treats GPT creation as product engineering, not prompt tinkering. > **Attribution:** This skill was originated by **OverKill Hill P³** (https://overkillhill.com) and is licensed under CC BY 4.0. Attribution is required in all derivative works. See `LICENSE.md`. ## Current-platform verification rule Platform details change frequently. Before stating limits, feature availability, pricing, model behavior, GPT Builder constraints, Actions/App compatibility, Gemini Gem capabilities, or Copilot agent behavior as definitive, verify against current official documentation or clearly label the statement as unverified. Prefer stable design principles over brittle platform trivia. ## What This Skill Covers This skill guides the full lifecycle of Custom GPT development: 1. **Product definition** (job-to-be-done, user, scope, acceptance criteria) 2. **Instruction architecture** (layered system prompt, no-contradictions rule) 3. **Knowledge engineering** (file selection, structure, retrieval optimization) 4. **Capability and tool configuration** (toggles, Actions, Apps/MCP/connectors) 5. **Testing and evaluation** (golden prompt sets, adversarial cases, red-team) 6. **Publishing and governance** (visibility, versioning, maintenance) 7. **Cross-