Agentic Design Patterns: Planner, Executor, Reviewer | Echelon Deep Research
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Engineering & Architecture
13 min
2026-02-15

Agentic Design Patterns: Planner, Executor, Reviewer

An exploration of multi-agent architectures where distinctly prompted LLMs debate and verify each other before acting.

E
Echelon Advising
Autonomy Research Group

Executive Summary

  • Single zero-shot prompts hit a hard ceiling on reasoning capabilities.
  • Breaking tasks down using frameworks like LangGraph or AutoGen significantly boosts complex problem-solving accuracy.
  • The standard triad: A 'Planner' breaks down the user request, an 'Executor' calls the APIs, and a 'Reviewer' checks for errors.
Complex Task Success Rate
+42%Agentic vs Zero-Shot

The measured improvement when using a multi-agent debate framework compared to a single monolithic prompt.

1. The Monolithic Failure

Asking one LLM to 'Write an API integration, test it, and deploy it' results in spaghetti code and hallucinated endpoints. The context window becomes polluted with conflicting instructions.

Accuracy on Complex Reasoning (SWE-Bench)

Single Prompt (GPT-4)13
Chain of Thought Prompting28
Multi-Agent Iterative Loop55

The Reviewer Loop

The 'Reviewer' agent acts as the discriminator. It is given a strict rubric. If the 'Executor' fails the rubric, the Reviewer returns an error block, forcing the Executor to try again inside a managed while-loop.

2. Managing State

Agentic systems require rigorous state management (often recorded in an SQLite database or Redis). If the agents get lost in an infinite argument loop, the orchestrator must kill the thread after N iterations.

3. Specialized Tool Assignment

Instead of giving 20 tools to one AI, you give 1 tool to 20 specialized micro-agents. The 'Database Analyst' agent only has SQL access; the 'Web Scraper' agent only has browser access. This strict separation of concerns massively reduces hallucination.

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