OpenAI Assistants API
In one line
OpenAI's Assistants API is the company's hosted toolkit for building agents — bundling tool use, files, memory and the execution loop into one managed service.
Going deeper
The Assistants API is OpenAI exposing the agent capabilities behind ChatGPT to outside developers. Tool use, file search, code interpreter and thread-based memory come bundled, so you can ship an agent without hand-rolling the ReAct loop.
For marketers it is the fastest path to a working prototype inside the OpenAI ecosystem. The trade-off is vendor lock-in, which is why more teams are pairing it with vendor-neutral standards like MCP.
Since 2025 OpenAI has been splitting the API into separate products — Agents SDK, Realtime API and friends. The naming moves often, so check the latest docs before you commit to an interface.
Related terms
MCP
MCP (Model Context Protocol) is the open standard introduced by Anthropic for connecting LLMs to external tools and data sources in a consistent way.
AI AgentTool Use
Tool use is an LLM calling external APIs, calculators or search systems directly to ground its answers — the foundational behaviour of every agent.
LLMFunction Calling
Function calling is the interface that lets an LLM invoke predefined functions or APIs instead of just replying in natural language — the core mechanism behind AI agents.
AI AgentLangChain
LangChain is the most widely used open-source framework for building LLM apps and agents, bundling prompts, tools, memory and execution flow into composable modules.
AI AgentAI Agent
An AI agent is an LLM-driven system that takes a goal, plans the steps, calls the tools it needs and runs the task end-to-end with limited human input.
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