What documentation should exist for segmentation rules?

Your email lead leaves. The person who takes over opens your ESP and finds 150 segments with no context. Which ones are active? What's the logic behind "Engaged Tier 1"? Why does "Legacy Import 2022" exist and who's in it? Without documentation, answering any of those questions takes hours of detective work. With it, onboarding someone new to your segmentation setup takes about 20 minutes.

For each segment that's actively used in campaigns or automations, document: the rule logic in plain language (not a screenshot of the filter builder, which goes out of date), the intended audience and use case, any field dependencies that might break if the underlying data changes, and which campaigns or flows reference it. Two to three sentences covering these points is usually enough per segment.

A spreadsheet with columns for segment name, status (live/archived/test), rule summary, field dependencies, owner, and last reviewed date is the simplest format that works. Keep it somewhere shared so anyone on your team can find and edit it. Build the habit of updating it whenever a segment changes. When you run a list hygiene review or do a field migration, update the segment docs at the same time so they don't fall behind.

Your documentation should also cover the meta-rules: what thresholds you use for engagement tiers, how you define active vs. lapsed, and whether overlapping segments are allowed or avoided by design. These conventions help future team members build new segments that fit the existing system rather than creating ones that quietly conflict with what's already there. Review My Emails can help you validate segment accuracy before campaigns go live. Schedule a quarterly documentation review so the records stay current as your program evolves.