Electrical requirements
Specify phase, winding type, rating, primary voltage, secondary voltage and frequency. For multiple outputs, include per-output demand and simultaneous use. If the rating is unknown, provide load VA or current and starting information.
Mechanical requirements
List size limits, mounting-hole locations, terminal orientation, lead arrangement and any enclosure requirement. Include the nameplate and dimensional drawing for replacements, clearly marking dimensions that cannot change.
Order and delivery requirements
Include quantity, requested delivery date and destination country. If a sample will lead to repeat orders, indicate expected ordering frequency. State required approvals and documents at the outset so supply feasibility can be reviewed.
Unresolved requirements can be discussed
You do not need every item finalized to start a discussion. Send the requirements and intended use you already know. Open items can be clarified before manufacturing against the agreed specification and approved documents.