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MCP vs RAG vs AI Agents
To understand modern AI systems, you need to understand how these three pieces fit together.
𝗥𝗔𝗚 = “𝗚𝗶𝘃𝗲 𝘁𝗵𝗲 𝗺𝗼𝗱𝗲𝗹 𝗯𝗲𝘁𝘁𝗲𝗿 𝗮𝗻𝘀𝘄𝗲𝗿𝘀”
RAG retrieves relevant data, injects it into the prompt, and generates a grounded response. It’s best when your problem is answering questions using your docs, reducing hallucinations, or showing sources and citations. RAG improves what the model knows, not what it can do.
If you’re building with these patterns, here's a great guide on scaling multi-agent RAG systems: lucode.co/multi-agent-ra…
𝗠𝗖𝗣 = “𝗦𝘁𝗮𝗻𝗱𝗮𝗿𝗱𝗶𝘇𝗲𝗱 𝘁𝗼𝗼𝗹 𝗮𝗻𝗱 𝗱𝗮𝘁𝗮 𝗮𝗰𝗰𝗲𝘀𝘀”
MCP is a standardized interface between LLMs and external systems like APIs, databases, and apps. Use it when your model needs to query data, call services, or interact with real systems (Slack, GitHub, etc). MCP doesn’t decide actions, it defines how tools are exposed.
𝗔𝗜 𝗔𝗴𝗲𝗻𝘁𝘀 = “𝗠𝗮𝗸𝗲 𝘁𝗵𝗲 𝗺𝗼𝗱𝗲𝗹 𝘁𝗮𝗸𝗲 𝗮𝗰𝘁𝗶𝗼𝗻”
Agents operate in a loop: observe → plan → act → repeat, often using tools and memory. Use them when your problem requires multi-step reasoning, tool usage with verification, or full task execution. Agents start where RAG stops, turning decisions into actions and outcomes.
The simple mental model:
RAG → knowledge layer
MCP → tool layer
Agents → execution layer
Not every system needs all three explicitly, but complex ones often combine them.
If you want to see what this looks like in practice, this guide walks you through building a scalable multi-agent RAG system.
Check it out: lucode.co/multi-agent-ra…
What else would you add?
♻️ Repost to help others learn AI.
🙏 Thanks to @Oracle for sponsoring this post.
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