Media kit
A media kit is the one-page document a creator sends brands: who the audience is, what formats she offers, what they cost, and evidence from past work. Its credibility lives in dated, verifiable numbers and dies in stale or invented ones. Monthly-updated figures with a visible 'as of' date signal an operator.
Worked example
One page: niche summary, per-platform followers and ER dated this month, three formats with from-prices, two past collaborations, contact.
Related: Rate card · Engagement rate
Full context in the guides, or measure it yourself with the free tools.