7 Major Patterns of Agentic AI Design

Pros and Cons Analysis

Pros

When the pattern combinations click into place, here's what becomes possible. Based on systems I've actually used:

Item	Details
Autonomous task handling	Multi-step workflows complete without intermediate intervention. Report generation that used to take our team 2 hours manually dropped to 20 minutes with an agent
Separation of expertise	Splitting roles with Multi-Agent raises quality in each domain
Real-world integration	Tool Use lets you leverage up-to-date information, databases, and external systems
Output quality control	Reflection catches errors internally before they reach the user
Safety assurance	Human-in-the-Loop lets you install guardrails on high-risk actions

Cons and Caveats

Honestly, I was too optimistic about this part at first and paid for it:

Item	Details	Mitigation
Cost spikes	Reflection more than doubles token usage; Multi-Agent multiplies LLM call counts — this is the thing that hit our team hardest early on	Apply selectively only where needed; set cost threshold alerts
Response latency	Longer loops accumulate latency	Identify steps that can run in parallel; set timeouts
Orchestration complexity	Inter-agent communication failures are hard to debug in Multi-Agent systems	Observability tools like LangSmith are a must
Plan error propagation	A bad plan from the Planning stage leads to total downstream failure	Add a plan validation step; execute only after confirming the plan
Security exposure	Tool Use abuse and Prompt Injection can trigger unintended tool calls	Minimize tool permissions, validate inputs, consider introducing a Guardian Agent

Prompt Injection: An attack technique where malicious input overwrites an LLM's system prompt or causes it to execute unintended commands. Particular caution is needed when an agent processes external data such as web search results or user input.

Guardian Agent: A dedicated agent that monitors other agents in real time for compliance violations, hallucinations, and scope drift. It is rapidly growing into an independent category within the 2025–2026 agentic AI ecosystem.

The Most Common Mistakes in Practice

Starting with Multi-Agent from day one: On my first agent project, I designed three agents — researcher, writer, and reviewer — simultaneously from the start. I spent far more time debugging context-passing issues between agents than I would have with a single-agent start. Starting simple and splitting off a role only when data confirms it is the bottleneck is far more effective.
Deploying to production without observability: Reproducing which reasoning step went wrong during 10 loops of agent execution without logs is practically impossible. Our team added LangSmith after the production deploy and spent two weeks unable to find a bug we would have fixed quickly if we'd caught it early. I strongly recommend wiring it in on day one of development.
Deferring Human-in-the-Loop to add later: The "automate first, add review steps later" approach forces you to redesign the architecture from scratch. In LangGraph, interrupt_before is decided at graph compilation time, so adding it later means reworking both the state design and the graph structure together. Define the list of hard-to-reverse actions early in the design phase and place checkpoints in front of them.

Closing Thoughts

The seven patterns are not independent solutions — they are a vocabulary to be combined according to the situation. Agent design truly begins not when you decide which pattern to use, but when you can explain why that pattern fits the problem at hand.

Three steps you can start right now:

You can implement a basic ReAct loop yourself with LangGraph — run pip install langgraph langchain-openai and execute the code examples above as-is. Watching the loop run with your own eyes is the fastest shortcut to understanding the concept.
You can connect LangSmith to visualize the agent's reasoning process — adding just one environment variable, LANGCHAIN_TRACING_V2=true, records every LLM call and tool usage in the dashboard. Create a free account at smith.langchain.com, get an API key, and you're connected instantly. Once you have observability, experimenting with pattern combinations becomes much easier.
You can pick one multi-step process your team handles manually and repeatedly, then map patterns to it — simply analyzing an existing workflow in pattern language — "this step is Sequential, Tool Use where external data is needed, Reflection where result validation is needed" — builds your instinct for agent design quickly.

References

#AgenticAI#LangGraph#ReAct#Multi-Agent#RAG#ToolUse#Reflection#Human-in-the-Loop#LLM#PromptInjection

7 Major Patterns of Agentic AI Design | DEV BAK - 기술블로그