Migrate to native @app.mcp_tool() decorators (azure-functions 1.25.0b2)

[Copilot]

Replaces generic_trigger/generic_*_binding pattern with first-class MCP decorators introduced in azure-functions 1.25.0b2. Removes ~100 lines of boilerplate JSON serialization and manual argument parsing.

Changes

Configuration:

• Pin azure-functions==1.25.0b2 in requirements.txt
• Add PYTHON_ISOLATE_WORKER_DEPENDENCIES: 1 to local.settings.json and bicep (required for new decorators)

Code simplification:

• Remove ToolProperty class and JSON serialization layer
• Replace @app.generic_trigger(type="mcpToolTrigger", ...) → @app.mcp_tool()
• Replace @app.generic_input_binding(type="blob", ...) → @app.blob_input(...)
• Replace @app.generic_output_binding(type="blob", ...) → @app.blob_output(...)
• Remove manual json.loads(context) and argument extraction
• Tool properties now inferred from function signatures; descriptions from @app.mcp_tool_property() or docstrings

Before:

@app.generic_trigger(
    arg_name="context",
    type="mcpToolTrigger",
    toolName="save_snippet",
    toolProperties=json.dumps([{"propertyName": "snippet", ...}]),
)
@app.generic_output_binding(arg_name="file", type="blob", ...)
def save_snippet(file: func.Out[str], context) -> str:
    content = json.loads(context)
    snippet = content["arguments"]["snippet"]
    file.set(snippet)

After:

@app.mcp_tool()
@app.mcp_tool_property(arg_name="snippet", description="The content of the snippet.")
@app.blob_output(arg_name="file", ...)
def save_snippet(file: func.Out[str], snippet: str) -> str:
    """Save a snippet to Azure Blob Storage."""
    file.set(snippet)

Net: -94 lines across function_app.py and README.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Migrate function_app.py from generic_trigger/generic_*_binding to new @app.mcp_tool() decorators (azure-functions 1.25.0b2)</issue_title>
<issue_description>## Summary

The sample currently uses @app.generic_trigger(type="mcpToolTrigger", ...) and @app.generic_input_binding / @app.generic_output_binding decorators with a manual ToolProperty helper class and JSON-serialized toolProperties. As of azure-functions==1.25.0b2, first-class MCP decorators are available that dramatically simplify this code. The sample should be updated to use them.

Motivation

• The current code requires a boilerplate ToolProperty class, manual JSON serialization of tool properties, and parsing context JSON to extract arguments — all of which the new decorators eliminate.
• The new decorators infer tool properties (name, type, description) directly from the Python function signature and docstrings, aligning with standard Python patterns.
• This sample is a quickstart template; it should showcase the latest recommended API surface.

Prerequisites / Environment Changes

src/requirements.txt

Pin the new beta version:

azure-functions==1.25.0b2

src/local.settings.json

Add the required worker isolation setting:

{
  "IsEncrypted": false,
  "Values": {
    "FUNCTIONS_WORKER_RUNTIME": "python",
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "PYTHON_ISOLATE_WORKER_DEPENDENCIES": "1"
  }
}

Deployed App Settings (infra / bicep / azd)

Ensure PYTHON_ISOLATE_WORKER_DEPENDENCIES: 1 is also set in the deployed Function App configuration (bicep / app settings).

---

Required Code Changes in src/function_app.py

1. Remove the ToolProperty helper class and all related boilerplate

Delete the entire ToolProperty class definition, the tool_properties_save_snippets_object / tool_properties_get_snippets_object lists, and the tool_properties_save_snippets_json / tool_properties_get_snippets_json JSON serialization lines. These are no longer needed — the new decorator infers tool properties from the function signature.

2. Migrate hello_mcp

Current:

@app.generic_trigger(
    arg_name="context",
    type="mcpToolTrigger",
    toolName="hello_mcp",
    description="Hello world.",
    toolProperties="[]",
)
def hello_mcp(context) -> None:
    return "Hello I am MCPTool!"

New:

@app.mcp_tool()
def hello_mcp() -> str:
    """Hello world."""
    return "Hello I am MCPTool!"

Key changes:

• @app.generic_trigger(...) → @app.mcp_tool()
• The tool description is now inferred from the function docstring.
• The toolName is inferred from the function name.
• No context arg is needed when the tool has no properties.
• Return type should be str, not None.

3. Migrate get_snippet

Current:

@app.generic_trigger(
    arg_name="context",
    type="mcpToolTrigger",
    toolName="get_snippet",
    description="Retrieve a snippet by name.",
    toolProperties=tool_properties_get_snippets_json,
)
@app.generic_input_binding(arg_name="file", type="blob", connection="AzureWebJobsStorage", path=_BLOB_PATH)
def get_snippet(file: func.InputStream, context) -> str:
    snippet_content = file.read().decode("utf-8")
    logging.info(f"Retrieved snippet: {snippet_content}")
    return snippet_content

New:

@app.mcp_tool()
@app.mcp_tool_property(arg_name="snippetname", description="The name of the snippet.")
@app.blob_input(arg_name="file", connection="AzureWebJobsStorage", path=_BLOB_PATH)
def get_snippet(file: func.InputStream, snippetname: str) -> str:
    """Retrieve a snippet by name from Azure Blob Storage."""
    snippet_content = file.read().decode("utf-8")
    logging.info(f"Retrieved snippet: {snippet_content}")
    return snippet_content

Key changes:

• @app.generic_trigger(...) → @app.mcp_tool()
• @app.generic_input_binding(...) → @app.blob_input(...); the type="blob" parameter is no longer needed (it is implicit).
• toolProperties JSON is replaced by @app.mcp_tool_property(...) input binding and/or function parameter type hints. Args in the function signature that don't map to another binding are automatically treated as MCP tool properties.
• context parameter is removed; MCP arguments are received as named function parameters (snippetname).

4. Migrate save_snippet

Current:

@app.generic_trigger(
    arg_name="context",
    type="mcpToolTrigger",
    toolName="save_snippet",
    description="Save a snippet with a name.",
    toolProperties=tool_properties_save_snippets_json,
)
@app.generic_output_binding(arg_name="file", type="blob", connection="AzureWebJobsStorage", path=_BLOB_PATH)
def save_snippet(file: func.Out[str], context) -> str:
    content = json.loads(context)
    snippet_name_from_args = content["arguments"][_SNIPPET_NAME_PROPERTY_NAME]
    ...

</details>



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- Fixes Azure-Samples/remote-mcp-functions-python#24

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