What is Tool Use? (Function Calling)

Tool use lets AI access external tools, APIs, and databases to complete tasks. Learn how function calling works and why it matters for brand visibility.

Tool use transforms AI from a static knowledge system into an active assistant that can browse the web, run code, query databases, make API calls, and interact with external services. When ChatGPT uses Bing to look up current stock prices or Claude writes and executes Python code, that's tool use in action. It's the bridge between what an AI knows and what it can do.

Why it matters

Tool use fundamentally changes how AI gathers and synthesizes information about your brand. When a customer asks an AI assistant for product recommendations, that AI might browse your website, check review platforms, query pricing databases, and pull from news sources - all in seconds. This creates a new visibility imperative: being present and accurate in tool-accessible sources. Traditional SEO optimized for human search. Now you also need to consider how your information appears when AI tools query it programmatically. The AI selecting which sources to include becomes a critical intermediary between your brand and potential customers.

What people get wrong

• Tool use means AI can access any system or database. AI can only use tools explicitly configured and authorized. Each tool requires specific integration work, authentication setup, and permission controls. An AI cannot arbitrarily access systems it hasn't been connected to.
• AI tools always return accurate, current information. Tool reliability varies significantly. Web browsing might return cached results, APIs can timeout or error, and the AI can misinterpret returned data. Results require the same scrutiny as any external data source.
• Plugins and tool use are the same as AI training. Tool use retrieves information at query time without changing the model's underlying knowledge. Unlike training, which permanently shapes the model, tool results are temporary context for a single conversation.

Related terms

AI Agent: Agents are the primary use case for tool use, chaining multiple tools together to complete complex autonomous tasks.

RAG: RAG is a specific type of tool use where the AI retrieves documents from a knowledge base before generating responses.

Real-Time AI Search: Real-time search is one of the most common tools, enabling AI to access current web content rather than relying on training data.

Track visibility where AI tools look

When AI systems use web browsing tools to answer queries about your industry, they're pulling from specific sources and forming responses that shape user perceptions. Trakkr monitors how your brand appears in these AI-generated responses, helping you understand which sources the AI trusts and where gaps in your visibility exist.