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AI workflow or agent: how to pick the right one for a task

Not every task needs an autonomous agent. For tasks with fixed inputs and outputs, a workflow may be enough. Use this decision table to choose based on predictability, exceptions, and permissions.

LeanX··4 min read

Also available in Korean: Read the Korean original

Short answer: If the inputs and outputs are fairly fixed, start with an AI workflow that follows a set sequence. Some tasks need different steps or tools each time. Only for those, consider an agent with narrow permissions and clear stop conditions.

When "agent" is the first word in an AI plan, the project tends to get harder than it needs to be. In practice, a lot of the work follows a sequence you can define ahead of time: summarizing, classifying, reformatting, drafting. For that work, a workflow may be enough. It makes it easy to see who made which decision.

Anthropic's guide to building effective agents distinguishes workflows from agents. Workflows follow pre-defined code paths. In agents, the model decides dynamically how to use tools and what steps to take. The guide also suggests starting with the simplest solution and adding complexity only when you need it. The decision table and the experiment order below are LeanX's suggestion. They adapt that idea to picking a task inside a team.

Ask how predictable the task is first

Instead of "will AI be good at this?" ask "can we explain this task?" Sorting new inquiries against fixed criteria and building a table is easy to explain, start to finish. A task where you pull material depending on the customer, compare several systems, and check back with someone is a different story. It has more branches.

Predictable doesn't mean risk-free. High-impact actions need human approval even inside a workflow. Think sending to a customer, payments, or changing permissions. Start with something reversible: reading, organizing, or a draft for review. Before you decide, record the repetition, the exceptions, and the approval points for the task you're considering.

Workflow vs. agent: a decision table

QuestionStart with a workflowConsider a narrow agent
SequenceYou can write down the steps and tool order in advanceThe research and tools needed differ case by case
OutputThe format is consistent: a table, a draft, a categoryYou need to compare several options and record why
ExceptionsYou can branch on rules or hand off to a personYou don't yet know the full range of exceptions
PermissionsRead-only or draft-only is enoughThe task needs tools, but approval, logging, and undo are ready

Answering "agent" in the right column even once doesn't mean you need one immediately. First check whether part of the research or comparison can still be pinned down as a workflow. "Sort inquiries into three categories, and flag anything unclear as needs review" is a workflow. "Search several documents and systems for evidence, draft an answer, and stop if there's no source" asks for broader judgment. It can still start as a draft-only task, though.

Five sentences to define your first experiment

Once you've picked a task, fill in the blanks below. Too many blank spots is a sign to break the task down further, not to shop for a tool. This is a team agreement, not a build spec.

This task starts when ________ happens.
The AI reads only ________ material.
The output is a draft in ________ format.
In case of ________, it stops and hands off to a reviewer.
It's done when ________ checks the source and the result.

Filling these in shows both what a workflow needs and what uncertainty an agent would have to handle. If the input isn't fixed, or there's no clear "done" condition, adding more agent capability won't make the result easier to evaluate. If a person keeps finding and comparing material in the same place every time, that narrow piece is worth testing as a limited search task.

What to check before adding complexity

If you want to give a task more tools and more autonomy than it started with, record the actual bottleneck from a real case first. Long wait times, repeated manual searching, and rules that conflict are reasons that justify a next step. Chaining several agents together because it "seems smarter" makes errors harder to trace.

If you do add an agent, scope its permissions to the job, tool by tool. Don't give reading, drafting, and external actions the same permission level. Keep the human approval point separate. Teams that need a shared standard for this should practice on common cases together before rolling it out further.

What to watch in the first two weeks

  • The share of results that pass your "done" criteria, and why people fixed the rest
  • Whether exceptions flagged "needs review" fed back into the task design
  • How long it takes a person to re-find the source and the result
  • Any action outside the intended permissions, or an unexpected external change

Workflow versus agent isn't a buzzword choice. It's a choice about where responsibility sits. Starting with a sequence you can explain makes quality easier to fix. It also makes the case for more complexity, if you ever need it, much clearer.

Where to start

Take one task and write the five sentences above. If many blanks stay empty, break the task into smaller parts before you choose any tool. Once every blank has a clear answer, use the decision table to pick a workflow or a narrow agent.

FAQ

What is an AI workflow?

It's a flow where the model and tools move through a set sequence and rules you define in advance. It fits classification, summarizing, and drafting tasks where the input and output stay fairly consistent.

When do you need an AI agent?

It can be considered when you can't pin down every tool or step in advance, and the task needs situational judgment in a narrow scope. Even then, set permissions and stop conditions first.

Should you chain multiple agents together from the start?

We don't recommend it. Confirm the result for one task and one review standard first. Add complexity only once you've confirmed a real quality problem or bottleneck. It's easier to manage that way.

Sources

  1. Anthropic, "Building Effective AI Agents"

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