Pydantic Deep Agents is a batteries-included agent harness that enables developers to build autonomous AI agents capable of tool-calling, sandboxed code execution, and multi-agent collaboration. It is built on top of Pydantic AI and provides support for the Model Context Protocol (MCP), state checkpointing, and skill management. The package includes a ready-to-use terminal AI assistant out of the box and serves as both a CLI tool and a framework for building production agents.