Cursor MCP: Three Ways to Add a Server
Cursor is the least painful MCP client to set up, and there are three ways in. A one-click install link, a settings screen, or a JSON file you write yourself. Most guides show you the JSON and stop, which is the slowest of the three and rarely the one you need.
The three routes, fastest first
One-click install links. Many MCP servers publish an install button in their docs. Clicking it hands off to Cursor, which opens a dialog with the name, transport, and URL already filled in. Confirm and you are done. No file, no terminal.
The settings UI. Open Cursor Settings → Tools & MCP → New MCP Server. Useful when the server you want has no install link, and it validates as you go rather than failing silently later.
The config file. Project-scoped configuration lives at .cursor/mcp.json in the repository. Global configuration lives at ~/.cursor/mcp.json. Both are read and merged.
Which config wins
The two files merge, and if the same server name appears in both, the project-level entry takes priority. That is the behavior to remember when a server behaves differently in one repository than another. Nothing is broken; the project file is shadowing your global one.
Practical division: put anything personal and cross-cutting in ~/.cursor/mcp.json, and check .cursor/mcp.json into the repository for servers the whole team needs.
The tool limit nobody warns you about
Cursor’s agent starts degrading past roughly 40 tools. Not with an error, which would at least be honest, but by picking the wrong tool as the context fills with options it has to consider.
This changes how you should think about adding servers. Five servers exposing a dozen tools each will make the agent worse, not better. Prefer a small number of servers that cover a lot of ground over many narrow ones, and disable servers you are not using in the current project.
What MCP adds, and what it does not
MCP has no trigger and no scheduler. Its own Triggers and Events working group opens by conceding that clients find out about server-side changes by polling, and that work is still listed as on the horizon rather than shipped. Carly supplies the missing half: connect it and the workflows that start on an event run behind whatever assistant you already use.
Cursor has its own automations that can start work from repository and workspace events, and they are useful. MCP is not that mechanism. A server you add is something the agent calls while you are working, so it extends reach rather than adding initiative.
Give Cursor one server that covers a lot of ground
Given the tool budget, a single server holding many accounts is worth more than several narrow ones. Carly is built that way: your mail, calendars, files, and business tools behind one MCP endpoint, with workflows that run on real events.
- Add your accounts to Carly. Sign in at carlyassistant.com, open Integrations, pick a service, click Connect, and authorize. Click Connect again for the next one and keep going for as many as you want. Carly connects to thousands of apps.
- Add Carly to Cursor. Open Cursor Settings → Tools & MCP → New MCP Server, or put this in
~/.cursor/mcp.jsonso it follows you across projects:
{
"mcpServers": {
"carly": {
"url": "https://carlyassistant.com/mcp/"
}
}
}- Use it in the flow you are already in. Check the calendar before promising a date, pull the thread describing the bug, file the outcome, without leaving the editor.
Free Zapier-style workflows; AI agents from $35/month. Connecting Carly costs nothing.
Frequently Asked Questions
How do I add an MCP server to Cursor?
Three ways: click a one-click install link from the server’s docs, use Cursor Settings → Tools & MCP → New MCP Server, or write the server into .cursor/mcp.json or ~/.cursor/mcp.json.
Where is Cursor’s mcp.json file?
.cursor/mcp.json for a single project, ~/.cursor/mcp.json globally. Both are merged.
Which config wins if a server is in both files?
The project-level .cursor/mcp.json entry takes priority over the global one when the names match.
How many MCP servers can Cursor handle?
There is no hard cap, but the agent gets noticeably worse at choosing the right tool past around 40 tools total, because the context fills with candidates.
Can a Cursor MCP server start work on its own?
No. MCP has no scheduler or event mechanism, so servers respond when the agent calls them.
More: Claude Code MCP · How to install an MCP server in 7 AI clients · Windsurf MCP · MCP servers: the complete list · What is MCP?
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