An agent-friendly form is a form whose role, fields, constraints, errors, confirmation and consequence are explicit enough to be understood by an AI agent.
It is not only a visually clean form. It must expose clear intent, labels connected to fields, coherent name attributes, associated error messages, a precise CTA and a confirmation that explains what happens next.
The test is simple: can a system understand what it must fill, why, in which context and what the submission will produce? If the answer depends on human intuition, the form is not agent-friendly yet.