How to Understand Why a Modded Effect Has No Description
Why Descriptions Are Missing
Just Enough Effect Descriptions scans every registered status effect and adds it to the Effects category automatically. However, it can only show a description if one exists. Vanilla effects have descriptions built in; many modded effects do not, because the mod author never added the required language entry. When you open such an effect, you'll see its name, icon, color, and source mod, but the description area will be empty or show a placeholder.
What You Can Still Learn
Even without a description, the detail page is useful. You can see which mod the effect belongs to, its color (helpful for identifying its particles), and any items the plugin detected as providers. For the actual gameplay behavior, check that mod's own documentation, in-game guidebook, or tooltips on the items that apply the effect.
If You Want to Add Descriptions Yourself
Modders add descriptions by placing a string in their language file using the key format effect.[mod_id].[effect_name].description. If you're editing a pack or your own mod, follow that same pattern so the plugin picks it up. The plugin reads these keys at load time, so the description appears the next time you open the effect's page. This is also how you'd add provider support for non-food items, since only foods are auto-detected.