The short answer
CallMcpTool is a name people report for the Cursor agent tool that calls an MCP server. Use Calculator Tools as that server when the file should be a public app. The URL is https://api.calculator.tools/mcp/. The publish call is webappCreate.
Cursor's own docs describe editing, search, terminal, and browser control. They do not publish one fixed list of tool names. This page follows a public forum report for the string CallMcpTool.
What this call does
In the report, Cursor's agent includes CallMcpTool next to ListMcpResources and FetchMcpResource. Those names are how that session labels MCP traffic. The agent uses them to run a tool on a server you already added.
CallMcpTool is not a host. It is the client call. If Calculator Tools is not in the MCP settings, the call has nowhere to publish a calculator.tools URL.
Cursor as a product is compared at Cursor.
What Calculator Tools does
Calculator Tools is the MCP server and the host. After you approve it, the agent can create an app and write files. You get a public URL on your account.
Files live in one directory. Static files only: HTML, CSS, JavaScript, and similar types.
You stay the owner. Free accounts can publish 3 apps. Pro ($5.99/month) raises the limit to 25.
How to use MCP for this job
In Cursor, add a custom MCP server with https://api.calculator.tools/mcp/. Sign in with Google. Click Approve.
Ask Cursor to publish a calculator. The agent reaches this server (sessions that show the name use CallMcpTool for that hop) and this server runs webappCreate, then webappfileCreate.
You can skip Cursor and open Create.
Other publish tools people add the same way include publish_site, create_site, and create_site_from_archive. Those hosts are not this account.
Limits
Calculator Tools does not rename Cursor's client tool. It does not confirm CallMcpTool as an official Cursor identifier. If your session uses another label, the server URL is what matters.
This host is not your git repo and not Cursor's browser. Check the app after publish.
Next step
Connect MCP in Cursor, or open Create. The first 3 apps are free.
Sources
Ready to publish a public app you own?
Calculator Tools