Prompts · Quality

Prompt Engineering Mistakes to Avoid (2026)

The most common prompt failures we still fix—plus patterns, schemas, and evals that keep agents and apps production-safe.

10 min read Fewer failures Production-ready
7Mistakes covered
5Production patterns
24/7Logging required
3Evals per change

Common mistakes

Production patterns to use

Schema + criteria: JSON outputs with explicit fields and quality bars.
Retrieval: Provide sources; require citations; refuse if insufficient.
Tooling: Use function calls for structured actions, not free-text.
Safety: Refusal rules, PII stripping, and approvals for risky actions.
Evals: Golden + synthetic tests before every release.

How we ship safely

  1. Define success: schema, constraints, and edge cases.
  2. Add retrieval, citations, and refusal logic.
  3. Version prompts + track lineage in Git.
  4. Run evals and regression tests; gate releases.
  5. Monitor logs, alerts, and cost; iterate quickly.
Prompts are product code. Treat them with specs, tests, and monitoring—or expect surprises in production.
Fix my prompts Talk to engineers

FAQ

Do small prompts need tests?

Yes—lightweight evals catch regressions and cost spikes early.

Which models to target?

Use small/fast models for simple tasks; reserve heavy models for reasoning.

How to manage versions?

Keep prompts in Git with changelog and linked eval results.

What about multi-turn?

Constrain memory, reset state intentionally, and test flows end-to-end.