Large Language Models (LLM) & AI Market: Developer Builds ProposalAI Using Two-Stage Prompting

A freelance developer built ProposalAI, a tool that reads Upwork job posts and generates tailored proposals, and published a technical breakdown of the prompt architecture. The author argues the key improvement is a two-stage approach—an initial structured signal extraction pass followed by a constrained proposal generation pass—which forces the model to reference the client's specific problem and avoid generic phrases. The project uses Next.js 14, Tailwind CSS, shadcn/ui, Supabase for backend and auth, GPT-4o for extraction reasoning, and Creem for payments. The live tool is available at proposalai.top. The article documents implementation details, sample prompts, and lessons learned from the developer's two-week build process.