The list you actually meant to send to.
The first thing agreed is what the file is for. The file is deduplicated against anything previously supplied to you. Every claim the file makes about itself can be checked against it.
Field population report
A per-column statement of how much is filled, delivered with the file rather than on request.
Repeatability
The same brief run twice produces the same file, because the definition is recorded.
Specification drafting
Writing down the field list, definitions and rules, so the same build can be repeated later.
A conversation about criteria is usually shorter than one about results.