diff --git a/crates/engine/src/lib.rs b/crates/engine/src/lib.rs
index 0872cd56..ce953a5a 100644
--- a/crates/engine/src/lib.rs
+++ b/crates/engine/src/lib.rs
@@ -476,6 +476,12 @@ pub struct Prefs {
     /// the Properties panel and the Control bar (their size fields pass `proportional` to
     /// `object.setBounds`).
     pub constrain_proportions: bool,
+    /// The tools' persistent options by store (a tool id, or a store a family shares: `liquify`
+    /// holds the Liquify tools' Global Brush Dimensions), see [`vectorcraft_tools::settings`]:
+    /// kept across tool switches and saved with the preferences. Not a Preferences dialog field:
+    /// resetting the preferences keeps them; `tool.setOption` edits them.
+    #[serde(skip_serializing_if = "std::collections::BTreeMap::is_empty")]
+    pub tool_settings: std::collections::BTreeMap<String, serde_json::Map<String, Value>>,
 }
 
 impl Default for Prefs {
@@ -609,6 +615,7 @@ impl Default for Prefs {
             web_export_settings: None,
             print_presets: vec![],
             constrain_proportions: false,
+            tool_settings: Default::default(),
         }
     }
 }
@@ -756,7 +763,8 @@ impl Session {
         if self.batch_stash.is_none() {
             let _ = self.cancel_interaction();
         }
-        self.tool = vectorcraft_tools::create(self.tool.id());
+        self.keep_tool_settings();
+        self.tool = self.make_tool(self.tool.id());
     }
     pub fn set_active(&mut self, index: usize) -> bool {
         if index < self.docs.len() {
@@ -1302,6 +1310,8 @@ mod tests_tileedge;
 #[cfg(test)]
 mod tests_tints;
 #[cfg(test)]
+mod tests_toolsettings;
+#[cfg(test)]
 mod tests_transparencygrid;
 #[cfg(test)]
 mod tests_units;
diff --git a/crates/engine/src/tests_toolsettings.rs b/crates/engine/src/tests_toolsettings.rs
new file mode 100644
index 00000000..49b930af
--- /dev/null
+++ b/crates/engine/src/tests_toolsettings.rs
@@ -0,0 +1,98 @@
+//! Tool options that persist across tool switches, documents and launches (`Prefs::tool_settings`).
+
+use serde_json::json;
+
+use super::*;
+
+fn session() -> Session {
+    let mut s = Session::new();
+    s.execute("file.new", &json!({"width": 800, "height": 600})).unwrap();
+    s
+}
+
+fn select(s: &mut Session, tool: &str) {
+    s.select_tool(tool, ViewInfo::default()).unwrap();
+}
+
+#[test]
+fn options_survive_a_tool_switch() {
+    let mut s = session();
+    select(&mut s, "mirrorCut");
+    s.set_tool_option("axis", &json!("horizontal"));
+    s.set_tool_option("keep", &json!("bottom"));
+    select(&mut s, "selection");
+    select(&mut s, "mirrorCut");
+    assert_eq!(s.tool_options(), json!({"axis": "horizontal", "keep": "bottom"}));
+    // Interaction state isn't kept: the Rotate tool's reference point starts afresh.
+    select(&mut s, "rotate");
+    s.set_tool_option("origin", &json!([10, 20]));
+    select(&mut s, "selection");
+    select(&mut s, "rotate");
+    assert_eq!(s.tool_options(), json!({"origin": null}));
+}
+
+#[test]
+fn liquify_tools_share_the_global_brush_but_not_their_own_options() {
+    let mut s = session();
+    select(&mut s, "warp");
+    s.set_tool_option("width", &json!(60));
+    s.set_tool_option("intensity", &json!(80));
+    s.set_tool_option("detail", &json!(7));
+    select(&mut s, "twirl");
+    let o = s.tool_options();
+    assert_eq!((o["width"].as_f64(), o["intensity"].as_f64(), o["detail"].as_f64()), (Some(60.0), Some(0.8), Some(2.0)));
+    s.set_tool_option("rate", &json!(-90));
+    select(&mut s, "warp");
+    assert_eq!(s.tool_options()["detail"], json!(7.0));
+    select(&mut s, "twirl");
+    assert_eq!(s.tool_options()["rate"], json!(-90.0));
+}
+
+#[test]
+fn another_tools_options_are_stored_and_shared_ones_reach_the_active_tool() {
+    let mut s = session();
+    select(&mut s, "warp");
+    let o = s.set_tool_option_cmd(&json!({"tool": "pucker", "values": {"width": 40, "height": 30, "detail": 5}})).unwrap();
+    assert_eq!((o["tool"].as_str(), o["detail"].as_f64()), (Some("pucker"), Some(5.0)));
+    assert_eq!((s.tool_id(), s.tool_options()["width"].as_f64(), s.tool_options()["detail"].as_f64()), ("warp", Some(40.0), Some(2.0)));
+    assert_eq!(s.tool_options_of("pucker")["height"], json!(30.0));
+    select(&mut s, "pucker");
+    assert_eq!(s.tool_options()["detail"], json!(5.0));
+    // `{}` reads the options; an unknown tool is an error.
+    assert_eq!(s.set_tool_option_cmd(&json!({})).unwrap(), s.tool_options());
+    assert!(s.set_tool_option_cmd(&json!({"tool": "nope", "key": "width", "value": 1})).is_err());
+}
+
+#[test]
+fn a_gesture_keeps_what_it_changed_and_a_document_switch_keeps_options() {
+    let mut s = session();
+    select(&mut s, "spiral");
+    s.set_tool_option("segments", &json!(14));
+    s.execute("file.new", &json!({"width": 300, "height": 300})).unwrap();
+    assert_eq!(s.tool_id(), "spiral");
+    assert_eq!(s.tool_options()["segments"], json!(14));
+    s.set_active(0);
+    assert_eq!(s.tool_options()["segments"], json!(14));
+}
+
+#[test]
+fn options_are_saved_with_the_preferences() {
+    let mut s = session();
+    select(&mut s, "polygon");
+    s.set_tool_option("sides", &json!(9));
+    select(&mut s, "selection");
+    let saved = serde_json::to_string(&s.prefs).unwrap();
+    assert!(saved.contains("toolSettings"), "{saved}");
+    // Next launch.
+    let mut t = session();
+    t.apply_prefs(serde_json::from_str(&saved).unwrap());
+    select(&mut t, "polygon");
+    assert_eq!(t.tool_options()["sides"], json!(9));
+    // Older preference files have none; none are written until a tool keeps something.
+    assert!(Prefs::default().to_json().get("toolSettings").is_none());
+    let old: Prefs = serde_json::from_value(json!({"keyboardIncrement": 2})).unwrap();
+    assert!(old.tool_settings.is_empty());
+    // Resetting the preferences keeps them.
+    t.execute("prefs.reset", &json!({})).unwrap();
+    assert_eq!(t.prefs.tool_settings["polygon"]["sides"], json!(9));
+}
diff --git a/crates/engine/src/tooling.rs b/crates/engine/src/tooling.rs
index a8a6cd13..172b22bd 100644
--- a/crates/engine/src/tooling.rs
+++ b/crates/engine/src/tooling.rs
@@ -1,10 +1,10 @@
 //! Hosting the active tool: pointer/key events → actions → commands.
 
-use serde_json::Value;
+use serde_json::{Map, Value};
 use vectorcraft_geom::Point;
-use vectorcraft_tools::{Action, Cursor, Mods, Overlay, PointerEvent, ToolContext, ToolKey};
+use vectorcraft_tools::{Action, Cursor, Mods, Overlay, PointerEvent, PointerKind, Tool, ToolContext, ToolKey, settings};
 
-use crate::{EngineError, Result, Session};
+use crate::{EngineError, Prefs, Result, Session};
 
 /// View state the tools need from the frontend.
 #[derive(Clone, Copy, Debug)]
@@ -56,10 +56,50 @@ impl Session {
         }
         let acts = self.with_tool_cx(view, |t, cx| t.deactivate(cx));
         self.apply_actions(acts)?;
-        self.tool = vectorcraft_tools::create(id);
+        self.keep_tool_settings();
+        self.tool = self.make_tool(id);
         Ok(())
     }
 
+    /// A fresh `id` tool with the options it keeps ([`settings`]): its last values, from this
+    /// session or a saved one.
+    pub(crate) fn make_tool(&self, id: &str) -> Box<dyn Tool> {
+        let mut t = vectorcraft_tools::create(id);
+        Self::restore_tool_settings(&self.prefs, t.as_mut());
+        t
+    }
+
+    /// Give `t` the persistent options stored for it in `prefs`.
+    fn restore_tool_settings(prefs: &Prefs, t: &mut dyn Tool) {
+        for (store, keys) in settings::stores(t.id()) {
+            let Some(saved) = prefs.tool_settings.get(store) else { continue };
+            for k in keys {
+                if let Some(v) = saved.get(*k) {
+                    t.set_option(k, v);
+                }
+            }
+        }
+    }
+
+    /// Store the persistent options of `t` in `prefs` (so they are saved with them too).
+    fn store_tool_settings(prefs: &mut Prefs, t: &dyn Tool) {
+        let opts = t.options();
+        for (store, keys) in settings::stores(t.id()) {
+            let saved = prefs.tool_settings.entry(store.to_string()).or_default();
+            for k in keys {
+                if let Some(v) = opts.get(*k) {
+                    saved.insert(k.to_string(), v.clone());
+                }
+            }
+        }
+    }
+
+    /// Keep the active tool's persistent options for the next time it, or a tool sharing them, is
+    /// made.
+    pub(crate) fn keep_tool_settings(&mut self) {
+        Self::store_tool_settings(&mut self.prefs, self.tool.as_ref());
+    }
+
     pub(crate) fn with_tool_cx<R>(&mut self, view: ViewInfo, f: impl FnOnce(&mut dyn vectorcraft_tools::Tool, &ToolContext) -> R) -> R
     where
         R: Default,
@@ -98,7 +138,7 @@ impl Session {
             Err(msg) => {
                 // A bug in the tool: start it afresh and drop its half-done drag.
                 let id = self.tool.id();
-                self.tool = vectorcraft_tools::create(id);
+                self.tool = self.make_tool(id);
                 let _ = self.cancel_interaction();
                 self.tool_panic = Some(EngineError::Internal { cmd: format!("tool `{id}`"), msg });
                 R::default()
@@ -116,6 +156,10 @@ impl Session {
         self.last_view = view;
         let acts = self.with_tool_cx(view, |t, cx| t.pointer(cx, ev));
         self.take_tool_panic()?;
+        // A gesture may change options (Alt-drag sizes a Liquify brush): keep them.
+        if ev.kind == PointerKind::Up {
+            self.keep_tool_settings();
+        }
         self.apply_actions(acts)
     }
 
@@ -162,6 +206,47 @@ impl Session {
     }
     pub fn set_tool_option(&mut self, key: &str, v: &Value) {
         self.tool.set_option(key, v);
+        self.keep_tool_settings();
+    }
+
+    /// The options of tool `id`: the active tool's, or those it would have if chosen now.
+    pub fn tool_options_of(&self, id: &str) -> Value {
+        if id == self.tool.id() { self.tool.options() } else { self.make_tool(id).options() }
+    }
+
+    /// Set options of tool `id` (default: the active tool). Another tool's persistent options are
+    /// stored for when it is chosen, and the active tool takes those it shares with it (the
+    /// Liquify tools' Global Brush Dimensions). Returns the tool's options.
+    pub fn set_tool_options(&mut self, id: Option<&str>, values: &Map<String, Value>) -> Value {
+        let active = id.is_none_or(|id| id == self.tool.id());
+        let mut other = (!active).then(|| self.make_tool(id.unwrap_or_default()));
+        let t = other.as_deref_mut().unwrap_or(self.tool.as_mut());
+        for (k, v) in values {
+            t.set_option(k, v);
+        }
+        Self::store_tool_settings(&mut self.prefs, t);
+        let out = t.options();
+        if other.is_some() {
+            Self::restore_tool_settings(&self.prefs, self.tool.as_mut());
+        }
+        out
+    }
+
+    /// `tool.setOption {tool?, key?, value?, values?}` (a command of the desktop app and of the
+    /// headless host): set one option (`key`, `value`) or several (`values`) of `tool` (default:
+    /// the active tool) → its options.
+    pub fn set_tool_option_cmd(&mut self, p: &Value) -> std::result::Result<Value, String> {
+        let tool = p.get("tool").and_then(Value::as_str);
+        if let Some(t) = tool
+            && vectorcraft_tools::tool_info(t).is_none()
+        {
+            return Err(format!("unknown tool `{t}`"));
+        }
+        let mut values = p.get("values").and_then(Value::as_object).cloned().unwrap_or_default();
+        if let Some(k) = p.get("key").and_then(Value::as_str) {
+            values.insert(k.to_string(), p.get("value").cloned().unwrap_or(Value::Null));
+        }
+        Ok(self.set_tool_options(tool, &values))
     }
 
     /// Let the active tool finish work a command from outside it ended ([`vectorcraft_tools::Tool::after_command`]):
diff --git a/crates/mcp/src/headless.rs b/crates/mcp/src/headless.rs
index 1bd0b46f..69ac0e41 100644
--- a/crates/mcp/src/headless.rs
+++ b/crates/mcp/src/headless.rs
@@ -38,6 +38,11 @@ const HOST_COMMANDS: &[(&str, &str, &str)] = &[
         "{folder?, zip?, artboards? | range? | fullDocument? | assets?, includeBleed?, subfolders?, preset?, formats?, settings?, prefix?} = document.exportForScreens (no folder → the files, or one zip, as dataBase64)",
     ),
     ("tool.select", "Select Tool", "{tool} e.g. selection, directSelection, pen, rectangle, ellipse, polygon, star, lineSegment"),
+    (
+        "tool.setOption",
+        "Tool Option",
+        "{key, value} | {values: {key: value…}}, tool?: id (default: the active tool) → the tool's options (`{}` reads them); kept options last across tool switches",
+    ),
 ];
 
 fn s<'a>(p: &'a Value, k: &str) -> Option<&'a str> {
@@ -113,6 +118,7 @@ impl Headless {
             "file.export" => self.export(params),
             "file.exportForScreens" => self.session.execute("document.exportForScreens", params).map_err(|e| e.to_string()),
             "tool.select" => self.select_tool(params),
+            "tool.setOption" => self.session.set_tool_option_cmd(params),
             _ => self.session.execute(id, params).map_err(|e| e.to_string()),
         }
     }
diff --git a/crates/mcp/src/tests_liquify.rs b/crates/mcp/src/tests_liquify.rs
new file mode 100644
index 00000000..572dc92f
--- /dev/null
+++ b/crates/mcp/src/tests_liquify.rs
@@ -0,0 +1,29 @@
+//! The Liquify tools through MCP: their options (`tool.setOption`, kept across tool switches) and
+//! brush strokes with `pointer_gesture`.
+
+use serde_json::{Value, json};
+
+use crate::{Headless, call_tool};
+
+fn ok(h: &mut Headless, name: &str, args: Value) -> Value {
+    let r = call_tool(h, name, &args);
+    assert!(!r.is_error, "{name} {args}: {r:?}");
+    serde_json::from_str(r.content[0]["text"].as_str().unwrap()).unwrap_or(Value::Null)
+}
+
+fn command(h: &mut Headless, command: &str, params: Value) -> Value {
+    ok(h, "run_command", json!({"command": command, "params": params}))
+}
+
+#[test]
+fn tool_options_are_set_headless_and_kept_across_tool_switches() {
+    let mut h = Headless::with_document();
+    command(&mut h, "tool.select", json!({"tool": "warp"}));
+    let o = command(&mut h, "tool.setOption", json!({"values": {"width": 64, "detail": 6}}));
+    assert_eq!((o["width"].as_f64(), o["detail"].as_f64()), (Some(64.0), Some(6.0)));
+    command(&mut h, "tool.select", json!({"tool": "bloat"}));
+    let o = command(&mut h, "tool.setOption", json!({}));
+    assert_eq!((o["tool"].as_str(), o["width"].as_f64(), o["detail"].as_f64()), (Some("bloat"), Some(64.0), Some(2.0)));
+    command(&mut h, "tool.select", json!({"tool": "warp"}));
+    assert_eq!(command(&mut h, "tool.setOption", json!({}))["detail"], json!(6.0));
+}
diff --git a/crates/tools/src/distort/liquify.rs b/crates/tools/src/distort/liquify.rs
index a02bf22f..ff747367 100644
--- a/crates/tools/src/distort/liquify.rs
+++ b/crates/tools/src/distort/liquify.rs
@@ -157,6 +157,16 @@ impl LiquifyParams {
         v
     }
 
+    /// Every option, whichever tool these are (the tool's options: [`Self::to_json`] gives only
+    /// the parameters its kind uses).
+    pub fn options_json(&self) -> Value {
+        let mut v = self.to_json();
+        for (k, x) in [("rate", self.rate), ("complexity", self.complexity), ("horizontal", self.horizontal), ("vertical", self.vertical)] {
+            v[k] = json!(x);
+        }
+        v
+    }
+
     fn radii(&self) -> (f64, f64) {
         (self.width / 2.0, self.height / 2.0)
     }
@@ -528,7 +538,7 @@ impl Tool for LiquifyTool {
         Cursor::Crosshair
     }
     fn options(&self) -> Value {
-        self.params.to_json()
+        self.params.options_json()
     }
     fn set_option(&mut self, key: &str, value: &Value) {
         let mut v = self.params.to_json();
diff --git a/crates/tools/src/lib.rs b/crates/tools/src/lib.rs
index 3b8fd60b..6030bfa2 100644
--- a/crates/tools/src/lib.rs
+++ b/crates/tools/src/lib.rs
@@ -23,6 +23,7 @@ pub mod pen;
 pub mod place;
 pub mod printtiling;
 pub mod select;
+pub mod settings;
 pub mod shape;
 pub mod slice;
 pub mod symbolism;
diff --git a/crates/tools/src/settings.rs b/crates/tools/src/settings.rs
new file mode 100644
index 00000000..38c92b3e
--- /dev/null
+++ b/crates/tools/src/settings.rs
@@ -0,0 +1,74 @@
+//! Tool options that persist: a tool keeps them when another tool is chosen and they are saved
+//! with the preferences, as the reference app keeps each tool's options. Options that are the
+//! state of an interaction (pins, a reference point, the text being edited, the files a place
+//! cursor holds) aren't listed: they start afresh.
+//!
+//! Each row names the tools it covers, the store their values live in and the option keys. A row
+//! with a shared store gives every tool it lists one set of values: the Liquify tools share their
+//! Global Brush Dimensions, the Symbolism tools their brush. Otherwise each tool has its own store,
+//! named after its id.
+
+/// (tools, the store they share (None: each tool's own), option keys).
+type Row = (&'static [&'static str], Option<&'static str>, &'static [&'static str]);
+
+/// The Liquify tools.
+pub const LIQUIFY: &[&str] = &["warp", "twirl", "pucker", "bloat", "scallop", "crystallize", "wrinkle"];
+
+const SYMBOLISM: &[&str] =
+    &["symbolSprayer", "symbolShifter", "symbolScruncher", "symbolSizer", "symbolSpinner", "symbolStainer", "symbolScreener", "symbolStyler"];
+
+const ROWS: &[Row] = &[
+    // Global Brush Dimensions.
+    (LIQUIFY, Some("liquify"), &["width", "height", "angle", "intensity"]),
+    (LIQUIFY, None, &["detail", "simplify", "rate", "complexity", "horizontal", "vertical"]),
+    (SYMBOLISM, Some("symbolism"), &["diameter", "intensity", "density"]),
+    (&["mirrorCut"], None, &["axis", "keep"]),
+    (&["puppetWarp"], None, &["showMesh", "expand"]),
+    (&["arc"], None, &["closed"]),
+    (&["spiral"], None, &["decay", "segments", "clockwise"]),
+    (&["rectangularGrid"], None, &["rows", "columns"]),
+    (&["polarGrid"], None, &["concentric", "radial"]),
+    (&["pencil", "paintbrush"], None, &["fidelity", "fill", "editWithin", "closeWithin"]),
+    (&["smooth"], None, &["fidelity"]),
+    (&["blobBrush", "eraser"], None, &["size"]),
+    (&["polygon"], None, &["sides"]),
+    (&["star"], None, &["points"]),
+    (&["freeTransform"], None, &["constrain"]),
+    (&["artboard"], None, &["moveArt"]),
+];
+
+/// The stores `tool`'s persistent options live in, each with the option keys it holds.
+pub fn stores(tool: &str) -> impl Iterator<Item = (&'static str, &'static [&'static str])> + '_ {
+    ROWS.iter().filter_map(move |(tools, shared, keys)| {
+        let id = tools.iter().find(|t| **t == tool)?;
+        Some((shared.unwrap_or(id), *keys))
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn every_listed_option_is_one_the_tool_reports() {
+        for (tools, _, keys) in ROWS {
+            for id in *tools {
+                assert!(crate::tool_info(id).is_some(), "{id} is a tool");
+                let opts = crate::create(id).options();
+                for k in *keys {
+                    assert!(opts.get(*k).is_some(), "{id} reports `{k}` in {opts}");
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn liquify_tools_share_the_global_brush() {
+        let warp: Vec<_> = stores("warp").collect();
+        let twirl: Vec<_> = stores("twirl").collect();
+        assert_eq!(warp[0], twirl[0]);
+        assert_eq!(warp[0].0, "liquify");
+        assert_eq!((warp[1].0, twirl[1].0), ("warp", "twirl"));
+        assert_eq!(stores("selection").count(), 0);
+    }
+}
diff --git a/crates/ui-egui/src/menus.rs b/crates/ui-egui/src/menus.rs
index 9003c03f..453cc25b 100644
--- a/crates/ui-egui/src/menus.rs
+++ b/crates/ui-egui/src/menus.rs
@@ -170,7 +170,12 @@ pub const UI_COMMANDS: &[(&str, &str, &str, &str)] = &[
     ("window.workspace.list", "List Workspaces", "", "{}"),
     ("window.newWindow", "New Window", "", "{}"),
     ("tool.select", "Select Tool", "", "{tool: id} (see tools)"),
-    ("tool.setOption", "Tool Option", "", "{key, value}"),
+    (
+        "tool.setOption",
+        "Tool Option",
+        "",
+        "{key, value} | {values: {key: value…}}, tool?: id (default: the active tool) → the tool's options (`{}` reads them). The options a tool keeps (Liquify brush and tool options, Mirror & Cut, Puppet Warp, drawing tools…) last across tool switches and are saved with the preferences; another tool's are stored for when it is chosen",
+    ),
     (
         "effect.dialog",
         "Effect…",
@@ -786,11 +791,7 @@ pub fn run_ui_command(app: &mut VectorcraftApp, id: &str, p: &Value) -> Option<R
             Some(t) => Err(format!("unknown tool `{t}`")),
             None => Err("missing `tool`".into()),
         },
-        "tool.setOption" => {
-            let k = s("key").unwrap_or_default();
-            app.session.set_tool_option(&k, p.get("value").unwrap_or(&Value::Null));
-            Ok(app.session.tool_options())
-        }
+        "tool.setOption" => app.session.set_tool_option_cmd(p),
         "effect.dialog" => crate::dialogs::open_effect_dialog(app, p),
         "ui.recolorDialog" => crate::dialogs::recolor::open(app, p),
         "ui.paramDialog" => {
diff --git a/docs/control-protocol.md b/docs/control-protocol.md
index 213c886f..114d6884 100644
--- a/docs/control-protocol.md
+++ b/docs/control-protocol.md
@@ -444,3 +444,8 @@ Colour adjustment effects (Effect → Color Adjustments) open the `effect` dialo
 Halftone… (`engine.execute {command: "ui.menuDialog", params: {command: "object.vectorHalftone"}}`) opens the
 `vectorHalftone` dialog (fields `shape`, `frequency`, `angle`, `mode`, `color`, `invert`, `clip`, `keepOriginal`,
 `preview`): it previews live and `ui.dialog.confirm` keeps the halftone as one undo step.
+
+Tool options last: `tool.setOption {key, value}` or `{values: {…}}` (and `tool` to set another tool's) sets them, and
+the options a tool keeps (Liquify brush and tool options, Mirror & Cut, Puppet Warp, Symbolism, drawing tools) stay
+when you switch tools or documents and are saved with the preferences. The Liquify tools share their Global Brush
+Dimensions (`width`, `height`, `angle`, `intensity`).
diff --git a/docs/mcp.md b/docs/mcp.md
index a85a2ae0..1a7486f2 100644
--- a/docs/mcp.md
+++ b/docs/mcp.md
@@ -1729,3 +1729,17 @@ font that became available redraws in it, without editing the document.
 {"name":"run_command","arguments":{"command":"text.fontList","params":{"family":"Source Serif 4"}}}
 {"name":"run_command","arguments":{"command":"text.rescanFonts","params":{}}}
 ```
+
+## Tool options
+
+`tool.setOption` reads and sets a tool's options, headless too: `{key, value}` or `{values: {…}}` sets them on the
+active tool, `tool` names another one, and `{}` just reads them; the result is the tool's options. The options a
+tool keeps last across tool switches (and documents) and are saved with the preferences (`toolSettings` in
+`prefs.get`'s full object), as the reference app keeps them: the Liquify tools' brush and tool options, Mirror & Cut's
+axis and side, Puppet Warp's mesh, the Symbolism brush, the line, grid, pencil, brush and eraser tools' options,
+polygon sides and star points. The Liquify tools share one set of Global Brush Dimensions (width, height, angle,
+intensity), and the Symbolism tools one brush. Interaction state (pins, a reference point) starts afresh.
+
+```json
+{"name":"run_command","arguments":{"command":"tool.setOption","params":{"tool":"twirl","values":{"width":60,"rate":90}}}}
+```