MCP Server Part 2: Represent callback-related data with a CallbackAdapter

[KoolADE85]

Summary

• Add CallbackAdapter: wraps a Dash callback and exposes MCP-related metadata (computed lazily)
  • It combines Dash's own callback map, layout, and user docstrings/types into 1 interface that the MCP server will use to present a complete picture of the app to LLMs.
• Add CallbackAdapterCollection for working with collections of adapters
• Add mcp_enabled parameter to @app.callback() for opting callbacks out of MCP
• Add mcp>=1.0.0 to dependencies

Manual testing

• You can inspect what kind of data the CallbackAdapter exposes
• you can run callbacks directly with run_callback (which is what MCP will do)

fromdashimportDash, html, dcc, Input, Outputfromdash._get_appimportapp_contextapp=Dash(__name__)
app.layout=html.Div([
dcc.Input(id="name", value="World"),
html.Div(id="greeting"),
])
@app.callback(Output("greeting", "children"), Input("name", "value"))defgreet(name):
"""Greet the user by name."""returnf"Hello, {name}!"withapp.server.app_context():
app_context.set(app)
fromdash.mcp.primitives.tools.callback_adapter_collectionimportCallbackAdapterCollectionfromdash.mcp.primitives.tools.callback_utilsimportrun_callbackcollection=CallbackAdapterCollection(app)
foradapterincollection:
print(f"Tool: {adapter.tool_name}")
print(f" Docstring: {adapter._docstring}")
print(f" Outputs: {[o['id_and_prop'] foroinadapter.outputs]}")
print(f" Inputs: {[i['name'] foriinadapter.inputs]}")
# Execute the callback through the adapteradapter=collection[0]
result=run_callback(adapter, {"name": "Alice"})
print(f"Callback result: {result}")

[github-actions]

Thank you for your contribution to Dash! 🎉

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

[T4rk1n]

Could add a generic here [TInput, TOutput]

[KoolADE85]

Even better: this function wasn't really needed anymore as most usages had been refactored away. I just refactored its last remaining user and this function is now removed.

[T4rk1n]

What are these code? This one has the same code as the base MCPError

[KoolADE85]

These are standard JSON-RPC error codes, as per the MCP spec on error handling.
I removed the redundant one.

[T4rk1n]

💃