MCP Server Part 3: Dash App Resources

[KoolADE85]

Summary

• Add read-only MCP resources:

  • dash://layout: retrieves the layout in the same json format as the _dash-layout endpoint
  • dash://components: retrieves a flat list of components which have IDs, along with their types
  • dash://pages: retrieves all pages from the page registry
  • dash://page-layout/{path}: a template for retrieving the layout of a specific page
  • dash://clientside-callbacks: describes all clientside callbacks for LLM discovery

• Resources may be conditionally listed (e.g. dash://pages only appears for multi-page apps)

Manual testing

from dash import Dash, html, dcc, Input, Output
from dash._get_app import app_context
import json

app = Dash(__name__)
app.layout = html.Div([
    dcc.Dropdown(id="city", options=["NYC", "LA", "Chicago"], value="NYC"),
    dcc.Graph(id="chart"),
])
@app.callback(Output("chart", "figure"), Input("city", "value"))
def update_chart(city):
    return {"data": [{"x": [1, 2], "y": [3, 4]}], "layout": {"title": city}}

with app.server.app_context():
    app_context.set(app)
    from dash.mcp.primitives.resources import list_resources, read_resource
    result = list_resources()
    for r in result.resources:
        print(f"Resource: {r.uri} — {r.name}")
    result = read_resource("dash://components")
    print(json.loads(result.contents[0].text))

[github-actions]

Thank you for your contribution to Dash! 🎉

This PR is exempt from requiring a linked issue due to its labels.

[T4rk1n]

Looks good overall, just wondering why the pages import wouldn't work since that is a pretty standard module.

[T4rk1n]

Why is this necessary if it only returns None? Seems like the modules are being used as a class, maybe refactor to a base class instead.

[KoolADE85]

That is a great idea! I added a base class and removed the no-op methods from each type of resource.

[T4rk1n]

Why would this import be not available?

[KoolADE85]

Good point - I guess it would always be there. I removed the defensive import and put it at the top.