In this tutorial, we demonstrate how to design a contract-first agentic decision system using PydanticAI, treating structured schemas as non-negotiable governance contracts rather than optional output formats. We show how we define a strict decision model that encodes policy compliance, risk assessment, confidence calibration, and actionable next steps directly into the agent’s output schema. By combining Pydantic validators with PydanticAI’s retry and self-correction mechanisms, we ensure that the agent cannot produce logically inconsistent or non-compliant decisions. Throughout the workflow, we focus on building an enterprise-grade decision agent that reasons under constraints, making it suitable for real-world risk, compliance, and governance…