Enough to start working it. Everything else — the study, the calls, the prototype — attaches to the lead afterwards.
Also becomes the pursuit's name. Rename it on the lead once the work has one.
Optional. Defaults to General until you know which part of the business is buying.
Where it came from is the strongest early signal about how to work it.
What they appear to need, in your own words. It can be a sentence.
Optional. Recorded as Unclassified until you set it.
Recorded against the buying unit, so they carry across every pursuit it has.