Sketch commands return the ids of the points, curves, constraints and dimensions they create as created: {points, curves, constraints, dimensions}, worked out in Session::execute from the sketch before and after, so a script can dimension and constrain new geometry right away; ids stay stable and are not reused after a delete (undo rewinds the counters with the design). The MCP execute tool describes the field

crates/engine/src/lib.rs

@@ -351,6 +351,7 @@ impl Session {
         let changed = !Arc::ptr_eq(&self.doc, &before.doc);
         match r {
             Ok(v) => {
+                let v = if changed { self.with_created(spec.id, params, &before, v) } else { v };
                 if changed {
                     if spec.undoable {
                         self.undo.push(before);
@@ -374,6 +375,28 @@ impl Session {
         }
     }
 
+    /// A sketch command's result gets `created`: the ids of the points, curves, constraints and
+    /// dimensions it added to its sketch (the `sketch` param, else the active sketch), so every
+    /// drawing and modify command reports them the same way (see `cmd::sketch_created`).
+    fn with_created(&self, id: &str, params: &Value, before: &Snapshot, mut v: Value) -> Value {
+        if !id.starts_with("sketch.") {
+            return v;
+        }
+        let Some(out) = v.as_object_mut() else { return v };
+        if out.contains_key("created") {
+            return v;
+        }
+        let named = match params.get("sketch") {
+            Some(Value::Number(n)) => self.doc.find_feature(&n.to_string()).map(|f| f.id),
+            Some(Value::String(x)) => self.doc.find_feature(x).map(|f| f.id),
+            _ => None,
+        };
+        let Some(sk) = named.or(self.active_sketch).or(before.active_sketch) else { return v };
+        let Ok(after) = self.doc.sketch(sk) else { return v };
+        out.insert("created".into(), cmd::sketch_created(before.doc.sketch(sk).ok(), after));
+        v
+    }
+
     /// Remember the design, active sketch and undo history; returns the checkpoint's id.
     pub fn checkpoint(&mut self) -> u64 {
         let id = self.next_checkpoint;