Create widgets from source

create_anywidget accepts Python source and constructs AnyWidgets from its final module namespace. Register it when a model should create an interface for the current task.

Run generated code in a sandbox

Supplied Python executes with the MCP server's permissions. Run this server in a disposable sandbox with scoped filesystem, network, credential, and process access. Each widget's JavaScript runs in the host's app iframe.

anywidget-mcp serve anywidget_mcp:create_anywidget --port 8010

Connect Inspector Chat and ask:

Create a counter widget with increment and decrement buttons. Expose its current value so we can discuss it after I interact with it.

The model supplies code and may select classes with classnames.

Select classes by name

The same factory can run directly in Python:

from anywidget_mcp import create_anywidget

code = """
import anywidget
import traitlets

class Counter(anywidget.AnyWidget):
    value = traitlets.Int(0).tag(sync=True)
    _esm = '''
    export default {
      render({ model, el, signal }) {
        const button = document.createElement("button");
        const draw = () => { button.textContent = model.get("value"); };
        button.addEventListener("click", () => {
          model.set("value", model.get("value") + 1);
          model.save_changes();
        }, { signal });
        model.on("change:value", draw);
        draw();
        el.append(button);
        return () => model.off("change:value", draw);
      }
    };
    '''
"""

widget = create_anywidget(code, classnames=["Counter"])

Names resolve in the namespace after the source finishes executing. Every selected binding must be an AnyWidget subclass with a zero-argument constructor. One class returns one widget. Several classes return widgets in the requested order and render together.

Omit classnames to select the last final binding to a source-defined, top-level AnyWidget class. Use explicit names when source defines several widgets or aliases. Compilation, class selection, and construction errors return the exception type and generated source line when available. The model can use that diagnostic to correct the source and retry. Direct Python calls raise a WidgetCreationError with the same message.

Source can define helpers, imports, and several classes in the same module. The module remains registered until every returned widget is closed or garbage-collected, so Python can resolve module references while the widgets are live.

The API reference lists arguments and errors.