What's an MCP server (Model Context Protocol) for proposals?

MCP is Anthropic's open standard letting AI assistants like Claude Desktop, Cursor, or ChatGPT call external tools — a proposals MCP server exposes operations (create template, fill document, send for signature, generate payment link) as tools the AI uses directly. ProposalMCP exposes 35+ tools across templates, documents, pricing, payment, and analytics, with deterministic CRUD operations free and AI calls scoped (rewrite_section beats regenerate_document).