Incorrect type definition for tools on vertexai.agent_engines.LangchainAgent #5786
Description
Submitting this issue before opening a PR to resolve it.
In vertexai.agent_engines.templates.langchain.py, the type definition for tools in the LangchainAgent class is Optional[Sequence["_ToolLike"]] = None,. However, _ToolLike is defined as _ToolsType, which itself is defined as _ToolsType = Sequence[_ToolType], so we are unnecessarily getting nested sequences. This causes mypy to give an error saying it expects elements (tools) of LangchainAgent(tools=[...]) to be of type Sequence.
Environment details
- OS type and version: macOS Sequoia 15.6.1
- Python version: 3.11.6
- pip version: 25.2
google-cloud-aiplatformversion: 1.111.