Install an MCP server by package name (npm/uvx), git URL, or local path. Writes config to selected AI clients and validates via MCP handshake.
AI agents use install_mcp_server to create or update resources in Cursor MCP Installer — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Cursor MCP Installer environment.
This tool installs software packages and writes configuration files to AI clients. While it is technically a Write operation (creating/modifying config files and installing packages), it carries high severity because it can introduce arbitrary code into the system via npm packages, git URLs, or local paths, and modify the configuration of AI clients.
From the tool's definition Install an MCP server by package name (npm/uvx), git URL, or local path. Writes config to selected AI clients and validates via MCP handshake.
Documented attack patterns abuse exactly the kind of access install_mcp_server gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Cursor MCP Installer, and nothing reaches the server without passing your rules. This is the rule we recommend for install_mcp_server:
{
"version": "1",
"default": "deny",
"tools": {
"install_mcp_server": {
"limits": [
{
"counter": "install_mcp_server_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}install_mcp_server stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
Free to start. No card required.
Install an MCP server by package name (npm/uvx), git URL, or local path. Writes config to selected AI clients and validates via MCP handshake. It is categorised as a Write tool in the Cursor MCP Installer MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Cursor MCP Installer MCP server in PolicyLayer and add a rule for install_mcp_server: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Cursor MCP Installer. Nothing to install.
install_mcp_server is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the install_mcp_server rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for install_mcp_server. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
install_mcp_server is provided by the Cursor MCP Installer MCP server (matthewdcage/cursor-mcp-installer). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Cursor MCP Installer, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
3 Cursor MCP Installer tools catalogued and risk-classified — across an index of 43,000+ MCP servers.