doc: Add how to add a new tool into README

README.md

@@ -30,6 +30,69 @@ new commits:
 
 ```bash
 uv run pre-commit install
-````
+```
 
-# Add a new tool
+# Adding new tools
+
+For the sake of clarity, we organize tools under the directory
+`tdagent/tools/`, and then add them to the `app.py` list of
+interfaces.
+
+As an example, let's create a tool that adds up two numbers. First,
+we create a new file `tdagent/tools/calc_tool.py` with the following
+content:
+
+```Python
+import gradio as gr
+
+
+def add_numbers(num1: float, num2: str) -> float:
+    """Compute the addition of two numbers `num1 + num2`.
+
+    Args:
+        num1: First number to add.
+        num2: Second number to add.
+
+    Returns:
+        The result of computing `num1 + num2`.
+    """
+    return num1 + num2
+
+
+gr_add_numbers = gr.Interface(
+    fn=add_numbers,
+    inputs=["number", "number"],
+    outputs="number",
+    title="Add two numbers",
+    description="Compute the addition of two numbers",
+)
+```
+
+Naming the file `calc_tool.py` is convenient as it let us add
+additional tools to calculate operations inside the same Python
+module.
+
+Then, we modify the `app.py` file to include our new tool.
+
+```Python
+import gradio as gr
+
+from tdagent.tools.get_url_content import gr_get_url_http_content
+...  # Other tools already present before
+from tdagent.tools.calc_tool import gr_add_numbers
+
+
+gr_app = gr.TabbedInterface(
+    [
+        gr_get_url_http_content,
+        ...,  # Other tools already present before
+        gr_add_numbers
+    ],
+)
+
+if __name__ == "__main__":
+    gr_app.launch(mcp_server=True)
+```
+
+In future updates we might change the `app.py` to automatically
+include any `gr.Interface`, but for now this works just fine.