Review fixes for #3042: "" with parse: false keeps the cell's formatting; correct the write_range parse description

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/cmd/edit/cell.rs

@@ -245,8 +245,8 @@ pub(super) fn range_set_values(s: &mut Session, p: &Json) -> Result<Json> {
                         if text.is_empty() {
                             // An empty string clears the cell, as `null` and the default path do:
                             // an empty text cell is not blank, and a script clearing cells with
-                            // `""` would leave cells `COUNTA` counts.
-                            None
+                            // `""` would leave cells `COUNTA` counts. The cell keeps its formatting.
+                            input_to_cell("", sheet, at, &mut cx.wb)?
                         } else {
                             let mut style = cx.wb.sheet(sheet).map(|sh| sh.style_id(at)).unwrap_or_default();
                             // Line breaks still turn on Wrap Text, as typed input does.

crates/engine/src/cmd/edit/tests.rs

@@ -225,10 +225,14 @@ fn set_values_parse_false_clears_an_empty_string() {
     let mut s = Session::new();
     s.new_workbook();
     s.execute("range.setValues", json!({"range": "A1:B1", "values": [["keep", "keep"]]})).unwrap();
+    s.execute("home.bold", json!({"range": "A1"})).unwrap();
     s.execute("range.setValues", json!({"range": "A1", "parse": false, "values": [["", ""]]})).unwrap();
     let get = |s: &mut Session, a: &str| s.execute("cell.get", json!({"cell": a})).unwrap();
     assert_eq!(get(&mut s, "A1")["type"], "empty");
     assert_eq!(get(&mut s, "B1")["type"], "empty");
+    let d = s.doc().unwrap();
+    let sh = d.wb.sheet(0).unwrap();
+    assert!(d.wb.styles.get(sh.style_id(CellRef::parse("A1").unwrap())).font.bold, "clearing with \"\" keeps the formatting");
     assert_eq!(s.execute("formulas.evaluate", json!({"formula": "=COUNTA(A1:B1)"})).unwrap(), json!(0.0));
 }
 

crates/mcp/src/tools.rs

@@ -196,7 +196,7 @@ fn base_tool_definitions() -> Vec<Value> {
                 json!({
                     "range": string("Top-left cell or range, e.g. \"A1\" or \"Sheet2!B3\""),
                     "values": {"type": "array", "description": "Rows of cell values", "items": {"type": "array", "items": {"type": ["string", "number", "boolean", "null"]}}},
-                    "parse": boolean("Store every string not starting with = as the text it is, instead of reading it like typed input (default true)"),
+                    "parse": boolean("Read strings not starting with = like typed input, so \"05.04.2026\" becomes a date (default true); false stores them as the text they are, and \"\" clears the cell"),
                 }),
                 &["range", "values"],
             ),