diff --git a/crates/ui-egui/src/dialogs.rs b/crates/ui-egui/src/dialogs.rs
index 093e88cd8..d027df9fd 100644
--- a/crates/ui-egui/src/dialogs.rs
+++ b/crates/ui-egui/src/dialogs.rs
@@ -1745,6 +1745,8 @@ fn format_cells(app: &mut SheetApp, ui: &mut egui::Ui, d: &mut Dialog, confirm:
     }
 }
 
+/// Insert Function: searches names (as the formula language spells them) and descriptions, shows
+/// each hit's category and description, and starts editing `=NAME(` (or appends to the formula).
 fn insert_function(app: &mut SheetApp, ui: &mut egui::Ui, d: &mut Dialog, confirm: &mut bool) {
     let language = app.ui.language;
     ui.horizontal(|ui| {
diff --git a/crates/ui-egui/src/formula_locale.rs b/crates/ui-egui/src/formula_locale.rs
index 11b551b10..c34e3cf86 100644
--- a/crates/ui-egui/src/formula_locale.rs
+++ b/crates/ui-egui/src/formula_locale.rs
@@ -160,10 +160,13 @@ pub(crate) fn display_template(text: &str, locale: FormulaLocale, wb: &Workbook,
 mod tests {
     use super::*;
 
+    /// The hint for `name`, empty when there is none.
     fn sig(name: &str, locale: FormulaLocale, language: Language) -> String {
         signature(name, locale, language).unwrap_or_default()
     }
 
+    /// Hints keep the formula syntax's name and separators and translate the argument names
+    /// only when the interface language has them all.
     #[test]
     fn function_help_follows_the_interface_language_and_the_formula_syntax() {
         use FormulaLocale::{En, Es};
diff --git a/crates/ui-egui/src/i18n.rs b/crates/ui-egui/src/i18n.rs
index 016441ced..fcc59bf3d 100644
--- a/crates/ui-egui/src/i18n.rs
+++ b/crates/ui-egui/src/i18n.rs
@@ -158,6 +158,7 @@ impl Language {
 /// English text and its translation, sorted by the English.
 type HelpTable = &'static [(&'static str, &'static str)];
 
+/// The translation of `english` in a help table (binary search, so the table must stay sorted).
 fn lookup(table: HelpTable, english: &str) -> Option<&'static str> {
     let i = table.binary_search_by(|(key, _)| (*key).cmp(english)).ok()?;
     table.get(i).map(|(_, translated)| *translated)
@@ -623,6 +624,7 @@ const JAPANESE: &[(&str, &str)] = &[
 mod tests {
     use super::*;
 
+    /// Help tables are sorted, unique, and keyed by text the function catalog still has.
     #[test]
     fn function_help_is_sorted_and_keyed_by_current_catalog_text() {
         // Lookups binary-search the tables. A key that no longer matches the catalog (an English
diff --git a/crates/ui-egui/src/ribbon.rs b/crates/ui-egui/src/ribbon.rs
index b25ce4b2e..f0b74089a 100644
--- a/crates/ui-egui/src/ribbon.rs
+++ b/crates/ui-egui/src/ribbon.rs
@@ -1749,6 +1749,8 @@ fn page_layout(app: &mut SheetApp, ui: &mut Ui) {
     }
 }
 
+/// The Formulas tab: Insert Function, AutoSum, the function-category menus (names in the formula
+/// language, descriptions in the interface language), defined names, auditing and calculation.
 fn formulas(app: &mut SheetApp, ui: &mut Ui) {
     let __k = big_button(ui, Icon::Function, "Insert\nFunction", "Insert Function (⇧F3)", false);
     control_keytip(app, ui, &__k, "dialog:insertFunction");