Part 4 · Engineering Patterns for Reliable Agents

Workflow vs Agent: Know What You Want First

Predefined flows vs model-driven decisions — Anthropic's two categories of Agent systems

THE QUESTION THIS PAGE ANSWERS

ANSWER FIRST

What is the key idea behind “Workflow vs Agent: Know What You Want First”?

Predefined flows vs model-driven decisions — Anthropic's two categories of Agent systems

DECISION RULE

Make the claim earn its place. Use this page as a decision aid, not a definition to memorize. Connect the idea to one real task, one observable result, and one failure that would change your mind.

TRY NEXT

Write one question you could answer with evidence after trying this idea.

WATCH FOR

A conclusion that sounds complete but leaves the key assumption untested.

Core Insight
"The most successful implementations weren't using complex frameworks or specialized libraries. Instead, they were building with simple, composable patterns."

Every AI product manager should commit this to memory. The industry is flooded with Agent frameworks (LangChain, AutoGen, CrewAI...), but production environments have repeatedly proven: the systems that work best use the simplest composable patterns.

Two Core Concepts
Workflow
LLMs and tools are orchestrated through predefined code paths. The developer decides the execution order at code-write time: do A, then B, then C.
Keywords: determinism, predictability, developer-controlled flow
Agent
The LLM dynamically determines its own execution flow and tool usage. At every step, the model autonomously decides what to do next, whether to call a tool, and when to stop.
Keywords: autonomy, dynamic decision-making, model-controlled flow
Flow Comparison
Workflow: Code-determined flow
Input
Step A
Step B
Output
Agent: Model-determined flow
Input
LLM Decision
Tool / Think / Re-decide
Output
Side-by-Side Comparison
Dimension Workflow Agent
Control Developer (fixed code path) Model (dynamic at each step)
Predictability High — same input, same execution path Low — same input may yield different paths
Best fit Well-defined tasks, fixed steps Open-ended tasks, flexible decisions needed
Cost Predictable (fixed number of calls) Uncertain (loop count unknown)
Debug difficulty Low (deterministic path, easy to reproduce) High (non-deterministic, hard to reproduce)
Typical examples Copywriting pipelines, data-cleaning pipelines Cursor, Claude Code, Devin
When NOT to Use an Agent
In most cases, you don't need an Agent
Practice shows: for most use cases, optimizing a single LLM call with Retrieval-Augmented Generation (RAG) is sufficient. Only when simpler solutions clearly cannot meet requirements should you consider introducing the complexity of Workflow or Agent.

A common over-engineering mistake: using an Agent framework to solve a problem that could be handled with one Prompt plus one search. The latency, cost, and non-determinism a framework introduces far outweigh its benefits.
Core Principle: The Complexity Ladder
Start with the simplest solution — add complexity only when it demonstrably improves outcomes
  • 1 Try a single LLM call first: optimize your Prompt, add Few-shot examples, tune Temperature
  • 2 Not enough? Add Retrieval-Augmented Generation (RAG): give the LLM access to external knowledge
  • 3 Still not enough? Use a Workflow: break the task into multiple steps and control the flow with code
  • 4 Genuinely need flexible decision-making? Only then reach for an Agent: let the model plan and execute autonomously
Not every problem needs an Agent — a Workflow often suffices, and sometimes a well-tuned Prompt is all you need. Complexity is a cost, not a feature. Only add complexity when it demonstrably delivers value.

Why “Core Insight” can find relevant content

“Every AI product manager should commit this to memory.” moves retrieval beyond storing material: the real question is how to find what is relevant. That decision shapes the input quality of RAG, recommendation, and image-search systems.

Similarity is not the answer

In the flow described by “Every AI product manager should commit this to memory.”, embeddings place items in a comparable semantic space and a neighbor index narrows the search. The final answer still depends on whether the retrieved chunks cover the question, whether the distance metric fits, and whether the evidence is current.

  • 1 Try a single LLM call first: optimize your Prompt, add Few-shot examples, tune Temperature
  • 2 Not enough? Add Retrieval-Augmented Generation (RAG) : give the LLM access to external knowledge
  • 3 Still not enough? Use a Workflow : break the task into multiple steps and control the flow with code

Separate findable from relevant

Turn “Every AI product manager should commit this to memory.” into a small test: prepare queries with known answers, record relevance, misses, and distractors, then decide whether chunking, the index, or reranking needs to change.

From “Core Insight” to “Two Core Concepts”

“Core Insight” grounds the problem in “Every AI product manager should commit this to memory. The industry is flooded with Agent frameworks (LangChain, AutoGen, CrewAI...), but production environments have repeatedly proven: the systems that work be…”. “Two Core Concepts” then moves it toward “Workflow LLMs and tools are orchestrated through predefined code paths . The developer decides the execution order at code-write time: do A, then B, then C. Keywords: determinism, predictability, developer-cont…”. Together, they show that the lesson is not just a conclusion to remember, but a claim with conditions.

Carry the judgment into the next situation

The same logic applies to retrieval: define what counts as relevant, check whether recall covers the question, and then inspect whether ranking, chunking, or freshness pushed useful evidence out.

  • “Core Insight”: Every AI product manager should commit this to memory. The industry is flooded with Agent frameworks (LangChain, AutoGen, CrewAI...), but production environments have repeatedly proven: the systems that work be…
  • “Two Core Concepts”: Workflow LLMs and tools are orchestrated through predefined code paths . The developer decides the execution order at code-write time: do A, then B, then C. Keywords: determinism, predictability, developer-cont…
  • “The closing point”: 4 Genuinely need flexible decision-making? Only then reach for an Agent : let the model plan and execute autonomously

The final “The closing point” brings the discussion to “4 Genuinely need flexible decision-making? Only then reach for an Agent : let the model plan and execute autonomously”. The useful thing to carry forward is knowing which judgments must be revisited when input, scale, or risk changes.

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ARTICLE DISCUSSION

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Discussing Workflow vs Agent: Know What You Want First Engineering Patterns for Reliable Agents
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AM
Asha MorganContent editor
INSIGHTField note

I turned one judgment from this article into a small experiment I could run today. Knowing what to observe next is more useful than simply remembering the conclusion.

ARTICLE DISCUSSION7 helpful
LH
Lin HarperIndie developer
INSIGHTInsight

After reading this, I first looked for the conditions behind the idea instead of copying the method into a project. That order made the later trade-offs much clearer.

ARTICLE DISCUSSION5 helpful
KM
Kiki MooreProduct operations
QUESTIONQuestion

When this judgment reaches real work, which constraint should be added first? I am curious which step matters most between reading and the first practical attempt.

ARTICLE DISCUSSION4 helpful