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No free plan. The cheapest way in is SDK at Free/open source documentation and Python package; no separate SDK subscription found in official docs.. Consider free alternatives in the ai agent builders category if budget is tight.
OpenAI Agents SDK is used to build agentic AI applications in Python with managed tool calls, handoffs between agents, guardrails, sessions, tracing, and realtime or voice agent support.
The Responses API is lower-level, while the Agents SDK gives developers a higher-level runtime for agent behavior. The SDK includes a built-in agent loop that invokes tools, sends results back to the model, and continues execution until a final result is produced.
The official introduction lists 3 core primitives: Agents, Agents as tools or Handoffs, and Guardrails. Agents are LLMs equipped with instructions and tools, handoffs let agents delegate work to other agents, and guardrails validate inputs or outputs.
Yes. The documentation includes a Sessions section and lists several session implementations and extensions, including SQLAlchemySession, Async SQLite session, RedisSession, MongoDBSession, DaprSession, EncryptedSession, and AdvancedSQLiteSession.
The SDK itself is open source and free to install. Runtime costs are separate and depend on the selected model and tools. For example, OpenAI's API pricing page lists GPT-5.4 mini text tokens at $0.75 per 1M input tokens, $0.075 per 1M cached input tokens, and $4.50 per 1M output tokens.
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Last verified March 2026