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App UIs are pure JSON-serializable component trees built from plain-function builders — no JSX, no client bundle: 
import { Column, Row, Text, Input, Button } from '@prefecthq/fastmcp-ts/server'

Column({}, [
  Text('Product Search'),
  Row({}, [
    Input({ name: 'query', placeholder: 'Search products…' }),
    Button({ label: 'Search', actionRef: 'run_search' }),
  ]),
])
This page is under construction. The outline below sketches what it will cover.
  • Builder catalog — layout (Column, Row, Grid), display (Text, Badge, Table, charts: Bar, Line, Area, Pie), input (Input, Select, Button), and control flow (If/.elif()/.else(), ForEach, Rx).
  • Actions — Button({ actionRef }) invokes backend tools; actionRef() resolves mount-prefixed names at execution time so apps work when mounted under a prefix.
  • Component model — every builder returns { type, props?, children? }; trees are plain data, easy to test and snapshot.
  • Conditional rendering — the If chaining API and how branches serialize.