Most AI agent failures don’t happen because the model isn’t “smart enough.” They happen because the system around them wasn’t built to succeed.
In my work building LLM agents, here’s what I encounter most often:
Unreliable prompt architecture
Agents usually depend on multiple prompts for planning, memory and tool use. Even minor formatting shifts can break robustness. You may need to test prompts systematically, tune them, or generate variants using the model itself.
Weak or missing evaluation strategy
Having no way to measure progress is like flying blind. Effective evals should go beyond end-to-end success. They must test components like tool calls, reasoning chains, and completion accuracy. Component level tracing helps isolate where things break.
Lack of safety and adversarial defenses
Prompt injection and memory poisoning are real threats: attacks often succeed in benchmarks. Basic defense prompts alone aren’t enough. Build robust safety audits and testing frameworks.
Poor system design or ambiguous spec
In multi-agent setups, many failures come from vague task specs or unclear role handoffs. Misaligned workflows and weak termination logic often sabotage execution.
No human-in-the-loop or judge feedback loop
Automated “judge” LLM evals can drift, if you train one black box to evaluate another, you’re stacking assumptions. The same works for security. The best pipelines mix automated scoring with occasional human reviews to catch what machines miss.
Tool invocation confusion
If your agent can call APIs or plugins, the interface needs to be rock solid. JSON schemas or function signatures work much better than loose natural-language descriptions, you want predictable invocation formats.
How to Fix It
Start by drawing a clear roadmap: what’s the end goal, and which component is responsible for which part?
Build robustness one prompt at a time
Treat prompt design like a polished API. Use clear instructions, delimiters, role definitions, and log everything. Track variants over time to see what actually works.
Run component-level evals
Create traces for tool usage, step-by-step reasoning, and task completion. Test both happy paths and edge cases so you can pinpoint failures.
Add real safety checks
Simulate prompt injections and memory corruption. Run safety benchmarks and audit your agent’s attack surface regularly.
Clarify spec and roles
Write crisp specs for agents. Define “this agent does X, then passes to that agent,” and make termination conditions explicit. Use a failure taxonomy to guide your audit.
Hybrid evaluation loops
Use “LLM-as-a-judge” to scale reviews but spot-check with humans. Regularly calibrate the judge to stay accurate.
Standardize tool calls
Define tool schemas or function signatures, and embed that in context so agents know exactly how to call them. This avoids parsing confusion and silent failures.
Quick checklist
- Define end-to-end success criteria and component metrics.
- Freeze a prompt baseline and iterate with controlled experiments.
- Add staged safety tests before deployment.
- Require a human sign-off for high-risk decisions.
Have you run into any of these pain points while building agents?
Curious to hear if you’ve tried component-level evals or a prompt robustness test and whether it revealed something wild.