LangChain has introduced a new abstraction for more complex tool usage, allowing tools to accept multiple inputs of varying types, and has developed a new agent class compatible with these tools. Initially, LangChain's tool use was limited to single-string inputs per tool due to model constraints, but advancements in language models like GPT-4 have enabled more sophisticated interactions. The new "multi-action" agent framework enables agents to execute multiple actions, and the introduction of "Structured Tools" allows for complex interactions between language models and tools by wrapping functions that agents can interface with easily. These tools are defined by a unique name, description, arguments schema, and run functions, and they support various operations from arithmetic to API requests. LangChain has also released new tools for file management and web browsing, alongside guidance for implementing custom structured tools. The new tools are compatible with existing agents if they accept a single string argument, while more complex structured tools require customization for full compatibility with older agents.