Tool calling (also called function calling) is how a language model works with external systems. The model gets a list of tools with descriptions and parameters. When a task needs a tool, the model returns a call request instead of text: which function to run and with which arguments. The program runs the call and hands the result back to the model, which decides what to do next.
Examples of tools:
- Send a message or read a thread's history
- Create a task in a tracker
- Read a file in a repo
- Search the web or a knowledge base
Tool calling is what sets an AI agent apart from a chatbot that only replies. The MCP protocol helps connect tools in a common format.
An agent works with Pachca through the API: it sends messages, reads threads and creates tasks and reminders. To help the agent call methods correctly, there's Pachca CLI with command details via --help, Agent Skills and the OpenAPI spec.
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