Configuration

Cursor MCP v2.1 lets you connect AI agents to external tools — databases, GitHub, Figma, Slack — through a standardized protocol. This guide covers every setup path: Server Cards auto-discovery, the Cursor Marketplace, manual mcp.json configuration, transport selection, and the security changes enforced after two critical CVEs in early 2026. What Is MCP v2.1 and What Changed in Cursor MCP (Model Context Protocol) v2.1 is the latest revision of Anthropic’s open standard for connecting AI agents to external tools and data sources. In Cursor specifically, v2.1 arrived alongside Cursor 2.0 in late 2025 and introduced three breaking changes that affect every developer who previously configured MCP servers manually: mandatory per-tool approval by default, the Server Cards discovery format (.well-known/mcp.json), and first-class support for Streamable HTTP transport alongside the original stdio approach. As of Q2 2026, MCP has reached 97 million monthly downloads — a 970x increase in 18 months — and 9,400 published servers across four major registries, making proper setup hygiene more important than ever. The key behavioral shift in Cursor 2.0 is that Agent mode (Cmd+I / Ctrl+I) is now the only context where MCP tools can be invoked; Chat mode ignores them entirely. If you’ve been wondering why your MCP tools “disappeared,” this is almost certainly why. ...

CLAUDE.md is the project instructions file that Claude Code reads before every session — it’s the single most impactful configuration you can make. Drop it in your repo root, add your coding conventions and architecture notes, and Claude stops asking the same questions every session. What Is CLAUDE.md? The System Prompt for Your Codebase CLAUDE.md is a Markdown file that acts as a persistent system prompt scoped to your project. Unlike conversation-level instructions that disappear after compaction, CLAUDE.md is re-read from disk at the start of every session and after every context compaction event. Introduced by Anthropic in August 2025, the format caught on fast enough that competitors shipped their own versions — GEMINI.md, .cursorrules, AGENTS.md — within months. By early 2026, 71% of developers who regularly use AI agents were using Claude Code (Pragmatic Engineer Survey, 15,000 developers), and the CLAUDE.md pattern had become the de facto standard for project-level AI configuration. ...