Find AI agents, MCP servers and AI developer tools in the AgentIndex directory by keyword and/or category. Use this when the user describes a need ("MCP server for Postgres", "browser automation agent"); use get_trending instead to browse the best tools without a query. Every keyword must appear (case-insensitive) in the name, description, tags or category. Results are ordered by rank_score, highest first. Returns an array of {id, name, category, description, stars, website, github_url, tags, rank_score}; an empty array means no match, so retry with fewer or broader keywords. Pass an id to get_tool_detail for features, use cases and the install command.