The troubleshooting loop
- Name the gapWhat exactly is wrong with this output?
- Classify the causeMissing facts, ambiguity, shape, size or drift
- Apply one fixThe cheapest one that matches
- CompareIs this version better than the last?
Still wrong? Back to the top with what you learned
Five causes, five different fixes
Nearly every underperforming prompt traces back to one of five causes. They look similar from the outside — the answer is bad — and they respond to completely different treatments, which is why the sympathetic-sounding advice to “add more detail” fails so often.
| Symptom | Likely cause | The fix |
|---|---|---|
| Confident facts that turn out to be wrong | Claude never had the information | Attach the document; ask it to quote before it concludes |
| Generic, could-be-about-anyone output | No audience, purpose or context given | Say who it is for, why, and what good looks like |
| Right content, unusable shape | Format was never specified | State the format you want, not the one you don’t |
| Some instructions followed, others dropped | Too many requirements in one request | Split into steps; check each before moving on |
| Quality falls away late in a long chat | The thread has drifted or grown unwieldy | Start a fresh conversation with a clean brief |
The first cause is the one to internalise. Anthropic’s help documentation is direct about it: Claude can hallucinate, can produce fabricated quotations that read as authoritative, and can be out of date on recent events because of its training cutoff. No amount of rephrasing fixes an answer about a document Claude has never seen. The fix is not linguistic; it is to put the source in the conversation.
Which fix does this failure call for?
- Facts are inventedSupply the sourceAttach it; ask for quotes before conclusions
- Bland or off-targetAdd contextAudience, purpose, constraints, two examples
- Wrong shape or lengthSpecify the formatSay what to produce, positively stated
- Instructions droppedSplit the taskOne output per step, checked in turn
The cheap fixes, in the order to try them
Be explicit, and test it on a colleague. The documentation offers a memorable check: show your prompt to someone with minimal context on the task and ask them to follow it — if they would be confused, so will Claude. Where the order or completeness of steps matters, give them as a numbered list. And explain why a rule matters rather than just stating it; the documented example contrasts a bare “never use ellipses” with the same instruction plus the reason that the text will be read aloud by a speech engine that cannot pronounce them.
Say what you want, not what you don’t. “Do not use markdown” performs worse than describing the output you actually want — smoothly flowing prose paragraphs, say. You can also name the format with a tag, and the style of the prompt itself pulls the answer along: a prompt written in plain paragraphs tends to produce plain paragraphs.
Show examples. Three to five examples, wrapped in tags so they are unmistakably examples, is the documented guidance. They should be relevant to your real case, diverse enough to cover edge cases, and consistently structured. For anything where “good” is a matter of house style rather than of instruction — tone of voice, how a case note is written, what a decent summary looks like here — two or three real past examples beat a paragraph of adjectives.
Give the work structure. Wrapping distinct parts of a long prompt in descriptive tags — instructions, context, the input itself — helps Claude tell them apart when the prompt mixes all three. And with a long document, put the document above the question rather than below it; the documentation reports this ordering can improve performance substantially on long inputs.
Diagnosed, then rewritten
Vague — will disappointtext
Write a summary of our
Q3 performance for the
board.Diagnosed and rewrittentext
Attached: the Q3
management accounts.
Audience: nine
non-executive directors,
not finance people.
Write 400 words in four
short paragraphs:
result, what drove it,
what worsened, what we
are doing next.
Every number must come
from the attachment,
with the line quoted. If
a figure is not there,
write "not in pack".When the problem is invented facts
Hallucination has its own toolkit, and it is worth knowing by name because the exam asks about it. Give Claude explicit permission to admit uncertainty — a line telling it to say it does not have enough information to assess something confidently, rather than guessing. For a long document, ask it to extract exact quotes relevant to the question first, and to say so plainly when no relevant quotes exist, before it does anything else with them. Require citations: for each claim, a direct supporting quote, with any claim that cannot be supported removed.
Beyond that there are three heavier techniques. Ask for step-by-step reasoning before the answer, which exposes faulty logic you can see and challenge. Run the same prompt more than once and compare — inconsistency between runs is a strong signal something is being invented. And feed an output back as input to be verified or expanded, which catches contradictions. You can also restrict Claude explicitly to the documents provided rather than its general knowledge. The documentation closes with the caution that matters most: these techniques significantly reduce hallucination but do not eliminate it, so critical information still gets validated, especially for high-stakes decisions.
Traps the wrong answers are built from
| Tempting but wrong | Do this instead |
|---|---|
| Retyping the same request more forcefully | Name the failure first, then apply the one fix that matches it. |
| Adding examples to fix a factual error | Attach the source and require quoted evidence for each claim. |
| Writing “do not do X” instructions | Describe the output you want; positive instructions outperform prohibitions. |
| Changing four things at once and declaring victory | Change one element, compare with the previous output, keep the better one. |
| Trusting an anti-hallucination technique as a guarantee | Treat it as risk reduction and still validate critical information. |
You should now be able to
- State precisely what is wrong with an output before changing anything.
- Map a symptom to one of five causes and choose the matching fix.
- Apply the colleague test and positive format instructions to a weak prompt.
- Use quote-first and citation techniques against fabricated content.
- Iterate by changing one element at a time and comparing versions.