Can LangChain interact with databases and external APIs?

Yes, LangChain can interact with databases and external APIs. It provides built-in tools and modular components that enable developers to connect language models to structured data sources and web services. This allows applications built with LangChain to retrieve, process, and act on data from external systems, making it useful for tasks like dynamic querying, real-time data integration, and workflow automation.

For database interactions, LangChain offers utilities like the SQLDatabaseChain, which translates natural language queries into SQL commands. For example, a developer could configure the chain to connect to a PostgreSQL database, enabling users to ask questions like “Show me last month’s sales figures” in plain English. The chain generates the corresponding SQL query, executes it, and returns the results in a readable format. LangChain also supports document-oriented databases (e.g., Chroma for vector storage) for use cases like semantic search over custom datasets. Developers can extend these integrations by writing custom database wrappers or using ORM libraries like SQLAlchemy.

When working with external APIs, LangChain simplifies integration through its APIChain and agent-based workflows. The APIChain can be configured to handle REST API requests, such as fetching weather data from a service like OpenWeatherMap. For more complex scenarios, developers can create custom “tools” that wrap API calls, which LangChain agents can dynamically invoke based on user input. For instance, an agent might call a payment gateway API to process a transaction after detecting a user’s intent to complete a purchase. These tools can also handle authentication, rate limiting, and data formatting, abstracting boilerplate code so developers focus on business logic. By combining database and API interactions, LangChain enables applications like chatbots that check inventory (via a database) and schedule deliveries (via a shipping API) in a single workflow.