Foundations · Explore this field ↗ · Architecture · 2 min read
Flows, retrieval, and agents are different tools
Choose the least flexible mechanism that can safely complete the job.
Start with the consequence
The right architecture depends less on how natural the conversation should sound than on what a wrong turn can do. A deterministic flow is valuable when required fields, order, and legal wording matter. Retrieval-augmented generation is useful when the answer exists in changing documentation and the system must cite it. An agentic planner is appropriate when a user request genuinely needs several tools or steps whose sequence cannot be completely known in advance.
Mix modes within one journey
A useful support agent can use generation to restate a question, retrieval to find policy, a fixed decision table to determine eligibility, and a tool to open a case. That is not architectural impurity; it is separation of concerns. The interface should not expose this machinery, but operators should be able to see which mode produced each turn. Microsoft’s guidance describes orchestration as a planner over actions, topics, knowledge, and child agents. That power increases the need for explicit permissions and testable intermediate steps.
A routing test
For every task, ask three questions. Is the correct path enumerable? Is the answer contained in approved knowledge? Can the system cause an external change? Enumerable paths favor flows. Knowledge questions favor retrieval. External changes require typed tools, authorization, confirmation, and an audit trail. Use a planner only when it adds real value after those controls exist.
Failure mode
The common failure is ‘agent washing’: a normal answer bot is marketed as autonomous, or an open-ended planner is deployed where a form would be safer. Both confuse users and operators. Describe capability in verbs that can be demonstrated—find, summarize, draft, check, submit—then specify the boundary for each verb.
A boundary worksheet
List the top twenty user requests and mark each as explain, retrieve, decide, or change. For every change, name the system of record and approval step. For every explanation, name the source and what makes it current. Then identify requests that cross modes—for example, explaining a refund policy before opening a case. This worksheet turns vague agent ambition into a routing map. It also reveals where a simple link, search result, or form remains better than conversation. Complexity should enter only where it reduces user effort without weakening control.
Primary reading
Sources and limits
These links support the architecture, policy, or product behavior discussed above. Vendor documentation describes vendor features; it is not independent proof of performance. Current details should be rechecked before a production decision.