diff --git a/apps/deckcraft-cli/src/help.rs b/apps/deckcraft-cli/src/help.rs
index 1b76001f..4245172a 100644
--- a/apps/deckcraft-cli/src/help.rs
+++ b/apps/deckcraft-cli/src/help.rs
@@ -147,7 +147,7 @@ A presentation is edited by running commands on it:
   deckcraft-cli run --cmd 'slide.new={{\"title\":\"Q3 results\"}}' --save q3.deckcraft
 
 `deckcraft-cli help SUBCOMMAND`, or `deckcraft-cli SUBCOMMAND --help`, explains one subcommand;
-`deckcraft-cli help run` explains commands.",
+`deckcraft-cli help run` explains how to write a command.",
         list.join("\n")
     )
 }
diff --git a/apps/deckcraft-cli/src/main.rs b/apps/deckcraft-cli/src/main.rs
index 7b36288f..139b8e90 100644
--- a/apps/deckcraft-cli/src/main.rs
+++ b/apps/deckcraft-cli/src/main.rs
@@ -195,7 +195,7 @@ fn run(args: &[String]) -> Result<(), String> {
         match a.as_str() {
             "--in" => input = Some(it.next().cloned().ok_or("--in needs a file")?),
             "--sample" => sample = true,
-            "--cmd" => cmds.push(it.next().cloned().ok_or("--cmd needs ID[=JSON]")?),
+            "--cmd" => cmds.push(it.next().cloned().ok_or("--cmd needs COMMAND[=PARAMS]")?),
             "--save" => save = Some(it.next().cloned().ok_or("--save needs a path")?),
             "--export" => export = Some(it.next().cloned().ok_or("--export needs a path")?),
             "--print" => print = true,
diff --git a/crates/engine/src/cmd/mod.rs b/crates/engine/src/cmd/mod.rs
index 9cd8e4f1..58ad2407 100644
--- a/crates/engine/src/cmd/mod.rs
+++ b/crates/engine/src/cmd/mod.rs
@@ -33,6 +33,9 @@ pub struct CommandSpec {
     /// Where it lives: `["Home", "Font"]` (ribbon tab and group) or `["Arrange"]` (menu).
     pub menu: &'static [&'static str],
     pub shortcut: Option<&'static str>,
+    /// The parameters as `describe` and `commands` show them, read by [`parse_params`]: `?` marks
+    /// an optional key, a spaced ` | ` separates alternative sets of keys (so alternative values
+    /// are written unspaced, `ms|null`), `(…)` is a remark and `→` starts the answer.
     pub params: &'static str,
     pub enabled: Enabled,
     pub run: Run,
@@ -53,6 +56,7 @@ pub struct CommandInfo {
 }
 
 impl CommandSpec {
+    /// Holds because `Session::execute` skips the selection check when `id` or `ids` is given.
     pub fn acts_on(&self) -> Option<String> {
         let keys = param_keys(self.params).unwrap_or_default();
         let named = if keys.contains(&"ids") {
@@ -114,7 +118,7 @@ pub fn has_text(s: &Session) -> std::result::Result<(), String> {
     has_doc(s)?;
     if s.active().is_some_and(|d| d.selection.text.is_some()) { Ok(()) } else { Err(NO_TEXT_POINT.into()) }
 }
-/// Text editing or shapes with text selected (formatting commands apply to either).
+/// Text editing or selected shapes (formatting commands apply to either).
 pub fn has_text_or_shapes(s: &Session) -> std::result::Result<(), String> {
     has_doc(s)?;
     if s.active().is_some_and(|d| d.selection.text.is_some() || !d.selection.shapes.is_empty()) { Ok(()) } else { Err(SELECT_TEXT_OR_SHAPE.into()) }
diff --git a/crates/engine/src/cmd/table.rs b/crates/engine/src/cmd/table.rs
index e8abb05c..ea5b2207 100644
--- a/crates/engine/src/cmd/table.rs
+++ b/crates/engine/src/cmd/table.rs
@@ -32,7 +32,7 @@ pub fn specs() -> Vec<CommandSpec> {
             "Split Cells",
             ["Table Layout", "Merge"],
             None,
-            "{cell?: [r, c] (else the edited cell), id?} | {row: index, col: index, id?}",
+            "{cell?: [r, c] (else the edited cell), id?} | {row?: index, col?: index, id?}",
             has_selection,
             split
         ),
diff --git a/crates/mcp/src/server.rs b/crates/mcp/src/server.rs
index 9316fa45..710067cd 100644
--- a/crates/mcp/src/server.rs
+++ b/crates/mcp/src/server.rs
@@ -24,7 +24,7 @@ list_commands and run them with run_command (or several with batch). Typical flo
 {layout:\"titleAndContent\", title, body} → add_shape / add_text_box / insert_picture / insert_chart → \
 inspect_slide to read back ids, boxes and text → render_slide to look at the result. Shape ids are looked up on the \
 current slide. An inserted shape is selected; run_command edit.select {ids:[…]} selects others. format.* acts on \
-the selected text or shapes; shape.fill, shape.line and the other commands whose parameters list `ids` act on \
+the selected text or shapes; shape.fill, shape.line and the other shape commands whose parameters list `ids` act on \
 those shapes, else on the selected ones. Save with save_presentation (.deckcraft or .pptx).";
 
 /// Resource URIs.