diff --git a/src/a2ui.rs b/src/a2ui.rs
index dbbab70..c3456bc 100644
--- a/src/a2ui.rs
+++ b/src/a2ui.rs
@@ -69,12 +69,12 @@ const FUNCTIONS: &[&str] = &[
     "@index",
 ];
 
-pub(crate) const SYSTEM_PROMPT: &str = r#"A2UI local-chat rendering is enabled. Use the newest A2UI v1.0 protocol. You may present interactive native UI by emitting newline-delimited messages inside a fenced `a2ui` block. Keep ordinary prose outside the block. Use catalogId `https://ds4server.local/a2ui/v1_0/catalog.json`.
+pub(crate) const SYSTEM_PROMPT: &str = r#"A2UI local-chat rendering is enabled. Use the newest A2UI v1.0 protocol. Present UI only when it materially improves the answer; plain prose is preferred otherwise. Emit A2UI directly in the assistant response, never through `write` or another tool, as newline-delimited messages inside a fenced `a2ui` block. Keep ordinary prose outside the block. Use catalogId `https://ds4server.local/a2ui/v1_0/catalog.json`.
 
 Every line must be one JSON object with `version":"v1.0"` and exactly one of `createSurface`, `updateComponents`, `updateDataModel`, `deleteSurface`, `callFunction`, or `actionResponse`. Create a surface before updating it. Treat the current client metadata as authoritative: if its surfaces object is empty, prior surfaces in chat history were dismissed and you must create a new surface instead of updating them. Components are a flat adjacency list and the root component has id `root`. Compose complete UIs by combining basic components through container child ids; include every referenced child, tab child, and list template component. Reuse the active surfaceId to update it incrementally; never recreate an existing surface. `createSurface` may include initial `components`, `dataModel`, and `surfaceProperties`. For `actionResponse`, put `actionId` beside `version` and put only `value` or `error` inside `actionResponse`.
 
 Catalog components:
-- Basic: Text(text Markdown,variant), Image(url,description,fit,variant including avatar), Icon(name), Video(url,posterUrl), AudioPlayer(url,description), Divider(axis), Row/Column(children,justify start|center|end|spaceBetween|spaceAround|spaceEvenly|stretch,align start|center|end|stretch), List(children,direction,align), Card(child), Modal(trigger,content), Tabs(tabs[{title,child}]), Button(child,variant,action:{event:{name,context,wantResponse}}), TextField(label,value:{path},variant shortText|longText|number|obscured,placeholder), CheckBox(label,value:{path}), Slider(value:{path},min,max), DateTimeInput(label,value:{path},enableDate,enableTime,min,max), ChoicePicker(label,options[{label,value}],value:{path},variant multipleSelection|mutuallyExclusive,displayStyle checkbox|chips,filterable). Put numeric weight on direct Row/Column children to distribute available space.
+- Basic: Text(text Markdown,variant caption|body), Image(url,description,fit contain|cover|fill|none|scaleDown,variant icon|avatar|smallFeature|mediumFeature|largeFeature|header), Icon(name; safe examples: info|error|check|close|search|settings), Video(url,posterUrl), AudioPlayer(url,description), Divider(axis horizontal|vertical), Row/Column(children,justify start|center|end|spaceBetween|spaceAround|spaceEvenly|stretch,align start|center|end|stretch), List(children,direction vertical|horizontal,align start|center|end|stretch), Card(child), Modal(trigger,content), Tabs(tabs[{title,child}]), Button(child,variant default|primary|borderless,action:{event:{name,context,wantResponse}}), TextField(label,value:{path},variant shortText|longText|number|obscured,placeholder), CheckBox(label,value:{path}), Slider(value:{path},max,min,steps positive integer), DateTimeInput(label,value:{path},enableDate,enableTime,min,max), ChoicePicker(label,options[{label,value}],value:{path},variant multipleSelection|mutuallyExclusive,displayStyle checkbox|chips,filterable). Put numeric weight on direct Row/Column children to distribute available space.
 - Research: Chart(title,chartType bar|line|area|stackedBar|pie|donut,series[{label,value,segments}]), Table(title,columns,rows), Metric(label,value,detail,trend), Timeline(title,events[{time,title,description,status}]), Map(title,locations[{label,latitude,longitude,detail}]), MindMap(title,nodes[{id,label,children}]), Form(title,children,submitLabel,action). Use pie or donut for proportional breakdowns; donut displays the total in its center.
 - Shared fields: id, accessibility, weight, checks. Checks use {"condition":{"call":"required","args":{...}},"message":"..."}. Bind dynamic values with {"path":"/json/pointer"}. The renderer supports every function in the v1.0 Basic Catalog, including validation, formatting, logic, pluralize, openUrl, and @index. Input edits are local and synchronous. Agent events receive their resolved context and current data model. Server-initiated `callFunction` messages are supported.