Where agents stop
The usual blocker is not the form. It is the inbox. A signup that issues nothing until an emailed link is clicked cannot be completed by anything without a mailbox, which is most agents acting on someone's behalf.
The second blocker is the API key. A self-serve signup that still requires a human to click through a dashboard to generate credentials has moved the wall rather than removed it.
What to change first
Let an account do something useful before it is verified. Read-only access, a sandbox, a rate-limited key: enough to evaluate you, not enough to abuse you.
Then document credential issuance as an API call, not a click path. If a developer has to be told where to click, an agent cannot follow the instructions at all.
Count your required fields
Every required field is a chance for an autonomous buyer to hold information it does not have. A company size dropdown is trivial for a person and a dead end for an agent buying on behalf of someone who never mentioned it.
Ask for what you need to create the account. Ask for the rest later, when you have earned it.