Does Cursor need an MCP server for this, or is the URL enough?
The URL is enough: /ai carries the full REST reference, so the agent can register, provision, and verify with plain HTTP calls. Adding the Furrow MCP server (streamable HTTP or stdio) gives it the same operations as typed tools, which is nicer for ongoing changes.
Do I have to create the Furrow account myself?
No. The agent calls POST /api/register, Furrow emails you a 6-digit code, you paste it into the chat, and the agent receives a team-scoped token. That is the only human step.
What does the agent actually change in my code?
It edits your form markup: sets the action to your Furrow submit URL, adds a hidden _gotcha honeypot and an _ft timing field, and (if you gave it keys) the Turnstile widget. Nothing else — there is no SDK to install and no server route to add.