Free AI Prompt Gen is an open-source, local-first prompt engineering tool designed to transform raw ideas into structured instructions for various AI modalities. Unlike "black box" wrappers, this rule-based wizard assembles prompts directly in the user's browser to ensure transparency and privacy. The tool utilizes several established prompting frameworks, including RTF for concise briefs, CO-STAR for comprehensive communication plans, TAG for goal-oriented tasks, and APE. It offers specialized workflows for different model types: text models (ChatGPT, Claude, Gemini), image generators (Midjourney, Stable Diffusion, DALL·E), video tools (Sora, Runway, Pika), and coding assistants. To optimize performance across different architectures, the tool formats outputs using specific syntax, such as Markdown headers for ChatGPT, XML tags for Claude, and bold parameter blocks for Gemini. Users can manage subjects, lighting, camera dynamics, and constraints like aspect ratios or negative prompts. While the prompt assembly occurs locally, the tool provides an optional feature to use a user-provided API key for prompt refinement via meta-prompting. The platform is entirely free, requiring no sign-ups, and includes features for saving prompts, comparing "before-and-after" versions, and utilizing starter templates.