Add doc for how to customize an LLM Tool.

docs/how-to-guides/develop-a-tool/create-and-use-tool-package.md

@@ -165,3 +165,4 @@ Alternatively, you can test your tool package using the script below to ensure t
 [Customize your tool icon](add-a-tool-icon.md)  
 [Add category and tags for tool](add-category-and-tags-for-tool.md)  
 [Use file path as tool input](use-file-path-as-tool-input.md)  
+[Customize an LLM Tool](customize_an_llm_tool.md)  

docs/how-to-guides/develop-a-tool/customize_an_llm_tool.md

@@ -0,0 +1,60 @@
+# Customize an LLM Tool
+In this document, we will guide you through the process of customizing an LLM tool, allowing users to seamlessly connect to a large language model with prompt tuning experience using a `PromptTemplate`.
+
+## Prerequisites
+- Please ensure that your [Prompt flow for VS Code](https://marketplace.visualstudio.com/items?itemName=prompt-flow.prompt-flow) is updated to version 1.2.0 or later.
+
+## How to customize an LLM tool
+Here we use [an existing tool package](https://github.com/microsoft/promptflow/tree/main/examples/tools/tool-package-quickstart/my_tool_package) as an example. If you want to create your own tool, please refer to [create and use tool package](create-and-use-tool-package.md).  
+
+1. Develop the tool code as in [this example](https://github.com/microsoft/promptflow/blob/main/examples/tools/tool-package-quickstart/my_tool_package/tools/tool_with_custom_llm_type.py).
+- Add a `CustomConnection` input to the tool, which is used to authenticate and establish a connection to the large language model.
+- Add a `PromptTemplate` input to the tool, which serves as an argument to be passed into the large language model.
+
+    ```python
+    from jinja2 import Template
+    from promptflow import tool
+    from promptflow.connections import CustomConnection
+    from promptflow.contracts.types import PromptTemplate
+
+
+    @tool
+    def my_tool(connection: CustomConnection, prompt: PromptTemplate, **kwargs) -> str:
+        # Customize your own code to use the connection and prompt here.
+        rendered_prompt = Template(prompt, trim_blocks=True, keep_trailing_newline=True).render(**kwargs)
+        return rendered_prompt
+    ```
+
+2. Generate the custom LLM tool YAML.  
+    Run the command below in your tool project directory to automatically generate your tool YAML, use _-t "custom_llm"_ or _--tool-type "custom_llm"_ to indicate this is a custom LLM tool:  
+    ```
+    python <path-to-scripts>\tool\generate_package_tool_meta.py -m <tool_module> -o <tool_yaml_path> -t "custom_llm"
+    ```
+    Here we use [an existing tool](https://github.com/microsoft/promptflow/blob/main/examples/tools/tool-package-quickstart/my_tool_package/yamls/tool_with_custom_llm_type.yaml) as an example.
+    ```
+    cd D:\proj\github\promptflow\examples\tools\tool-package-quickstart
+
+    python D:\proj\github\promptflow\scripts\tool\generate_package_tool_meta.py -m my_tool_package.tools.tool_with_custom_llm_type -o my_tool_package\yamls\tool_with_custom_llm_type.yaml -n "My Custom LLM Tool" -d "This is a tool to demonstrate how to customize an LLM tool with a PromptTemplate." -t "custom_llm"
+    ```
+    This command will generate a YAML file as follows:
+
+    ```yaml
+    my_tool_package.tools.tool_with_custom_llm_type.my_tool:
+    name: My Custom LLM Tool
+    description: This is a tool to demonstrate how to customize an LLM tool with a PromptTemplate.
+    # The type is custom_llm.
+    type: custom_llm
+    module: my_tool_package.tools.tool_with_custom_llm_type
+    function: my_tool
+    inputs:
+        connection:
+        type:
+            - CustomConnection
+    ```
+
+## Use the custom LLM tool in VS Code extension
+Follow the steps to [build and install your tool package](create-and-use-tool-package.md#build-and-share-the-tool-package) and [use your tool from VS Code extension](create-and-use-tool-package.md#use-your-tool-from-vscode-extension).  
+
+Here we use an existing flow to demonstrate the experience, open [this flow](https://github.com/microsoft/promptflow/blob/main/examples/tools/use-cases/custom_llm_tool_showcase/flow.dag.yaml) in VS Code extension.  
+- There is a node named "my_custom_llm_tool" with a prompt template file. You can either use an existing file or create a new one as the prompt template file.  
+![use_my_custom_llm_tool](../../media/how-to-guides/develop-a-tool/use_my_custom_llm_tool.png)

docs/how-to-guides/develop-a-tool/index.md

@@ -9,4 +9,5 @@ create-and-use-tool-package
 add-a-tool-icon
 add-category-and-tags-for-tool
 use-file-path-as-tool-input
+customize_an_llm_tool
 ```

examples/README.md

@@ -81,7 +81,7 @@
 | [cascading-inputs-tool-showcase](tools/use-cases/cascading-inputs-tool-showcase/README.md) | [![samples_tools_use_cases_cascading_inputs_tool_showcase](https://github.com/microsoft/promptflow/actions/workflows/samples_tools_use_cases_cascading_inputs_tool_showcase.yml/badge.svg?branch=main)](https://github.com/microsoft/promptflow/actions/workflows/samples_tools_use_cases_cascading_inputs_tool_showcase.yml) | This is a flow demonstrating the use of a tool with cascading inputs which frequently used in situations where the selection in one input field determines what subsequent inputs should be shown, and it helps in creating a more efficient, user-friendly, and error-free input process |
 | [custom-strong-type-connection-package-tool-showcase](tools/use-cases/custom-strong-type-connection-package-tool-showcase/README.md) | [![samples_tools_use_cases_custom_strong_type_connection_package_tool_showcase](https://github.com/microsoft/promptflow/actions/workflows/samples_tools_use_cases_custom_strong_type_connection_package_tool_showcase.yml/badge.svg?branch=main)](https://github.com/microsoft/promptflow/actions/workflows/samples_tools_use_cases_custom_strong_type_connection_package_tool_showcase.yml) |  This is a flow demonstrating the use of a package tool with custom string type connection which provides a secure way to manage credentials for external APIs and data sources, and it offers an improved user-friendly and intellisense experience compared to custom connections |
 | [custom-strong-type-connection-script-tool-showcase](tools/use-cases/custom-strong-type-connection-script-tool-showcase/README.md) | [![samples_tools_use_cases_custom_strong_type_connection_script_tool_showcase](https://github.com/microsoft/promptflow/actions/workflows/samples_tools_use_cases_custom_strong_type_connection_script_tool_showcase.yml/badge.svg?branch=main)](https://github.com/microsoft/promptflow/actions/workflows/samples_tools_use_cases_custom_strong_type_connection_script_tool_showcase.yml) |  This is a flow demonstrating the use of a script tool with custom string type connection which provides a secure way to manage credentials for external APIs and data sources, and it offers an improved user-friendly and intellisense experience compared to custom connections |
-| [custom_llm_tool_showcase](tools/use-cases/custom_llm_tool_showcase/README.md) | [![samples_tools_use_cases_custom_llm_tool_showcase](https://github.com/microsoft/promptflow/actions/workflows/samples_tools_use_cases_custom_llm_tool_showcase.yml/badge.svg?branch=main)](https://github.com/microsoft/promptflow/actions/workflows/samples_tools_use_cases_custom_llm_tool_showcase.yml) |  This is a flow demonstrating how to use a `custom_llm` tool, `custom_llm` tool allows users to connect to a customized large language model which is fine-tuned by tool developer |
+| [custom_llm_tool_showcase](tools/use-cases/custom_llm_tool_showcase/README.md) | [![samples_tools_use_cases_custom_llm_tool_showcase](https://github.com/microsoft/promptflow/actions/workflows/samples_tools_use_cases_custom_llm_tool_showcase.yml/badge.svg?branch=main)](https://github.com/microsoft/promptflow/actions/workflows/samples_tools_use_cases_custom_llm_tool_showcase.yml) | This is a flow demonstrating how to use a `custom_llm` tool, which enables users to seamlessly connect to a large language model with prompt tuning experience using a `PromptTemplate` |
 
 
 ### Connections ([connections](connections))

examples/tools/tool-package-quickstart/my_tool_package/yamls/tool_with_custom_llm_type.yaml

@@ -1,6 +1,6 @@
 my_tool_package.tools.tool_with_custom_llm_type.my_tool:
   name: My Custom LLM Tool
-  description: This is a tool to demonstrate the custom_llm tool type
+  description: This is a tool to demonstrate how to customize an LLM tool with a PromptTemplate.
   type: custom_llm
   module: my_tool_package.tools.tool_with_custom_llm_type
   function: my_tool

examples/tools/use-cases/custom_llm_tool_showcase/README.md

@@ -1,5 +1,5 @@
 # Flow with custom_llm tool
-This is a flow demonstrating how to use a `custom_llm` tool, `custom_llm` tool allows users to connect to a customized large language model which is fine-tuned by tool developer. 
+This is a flow demonstrating how to use a `custom_llm` tool, which enables users to seamlessly connect to a large language model with prompt tuning experience using a `PromptTemplate`.
 
 Tools used in this flow:
 - `custom_llm` Tool

examples/tools/use-cases/custom_llm_tool_showcase/flow.dag.yaml

@@ -1,4 +1,10 @@
-inputs: {}
+inputs:
+  website_name:
+    type: string
+    default: Microsoft
+  user_name:
+    type: string
+    default: ""
 outputs:
   output:
     type: string
@@ -12,3 +18,5 @@ nodes:
     path: prompt_template.jinja2
   inputs:
     connection: basic_custom_connection
+    website_name: ${inputs.website_name}
+    user_name: ${inputs.user_name}

examples/tools/use-cases/custom_llm_tool_showcase/prompt_template.jinja2

@@ -1 +1,6 @@
-This is the prompt for my custom LLM tool.
+Welcome to {{ website_name }}!
+{% if user_name %}
+    Hello, {{ user_name }}!
+{% else %}
+    Hello there!
+{% endif %}