Building autonomous AI agents requires understanding memory management, tool calling, model selection, and workflow orchestration. Key challenges include context window limitations, tool confusion, long-term memory persistence, and model-specific behaviors. Microsoft Agent Framework provides abstractions for agent creation, middleware, and multi-agent workflows. Different models excel at different tasks—Anthropic models handle tool calling well, while OpenAI and Google models vary in logic capabilities. Critical practices include implementing evaluations before production, using classical engineering alongside AI, managing token costs, and never changing models without testing. Memory strategies like scratchpads, summarization, and temporal weighting help manage context. Multi-agent systems with smaller specialized models often outperform single large models.