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Diagnosing poor outputs

CCAO-F 7.111 min read · checked 21 September 2026

Task statementIdentify, diagnose, and resolve issues with underperforming prompts or poor outputs

The troubleshooting loop

  1. Name the gapWhat exactly is wrong with this output?
  2. Classify the causeMissing facts, ambiguity, shape, size or drift
  3. Apply one fixThe cheapest one that matches
  4. CompareIs this version better than the last?

Still wrong? Back to the top with what you learned

The loop is short on purpose. Change one thing, look at the result, and keep whichever version was better — guessing at three changes at once tells you nothing.

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.

SymptomLikely causeThe fix
Confident facts that turn out to be wrongClaude never had the informationAttach the document; ask it to quote before it concludes
Generic, could-be-about-anyone outputNo audience, purpose or context givenSay who it is for, why, and what good looks like
Right content, unusable shapeFormat was never specifiedState the format you want, not the one you don’t
Some instructions followed, others droppedToo many requirements in one requestSplit into steps; check each before moving on
Quality falls away late in a long chatThe thread has drifted or grown unwieldyStart 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is direct about it: Claude can hallucinate, can produce fabricated quotations that read as authoritative, and can be out of date on recent events because of its training cutoff.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?

What is wrong with the output?
  • Facts are invented
    Supply the sourceAttach it; ask for quotes before conclusions
  • Bland or off-target
    Add contextAudience, purpose, constraints, two examples
  • Wrong shape or length
    Specify the formatSay what to produce, positively stated
  • Instructions dropped
    Split the taskOne output per step, checked in turn
Ask what kind of wrong it is before you touch the prompt. The commonest mistake is applying the second branch’s fix to the first branch’s problem.

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".
Four changes, each answering a named failure: no audience, no source, no format, no length. The rewrite is longer because each line replaces a guess.

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 wrongDo this instead
Retyping the same request more forcefullyName the failure first, then apply the one fix that matches it.
Adding examples to fix a factual errorAttach the source and require quoted evidence for each claim.
Writing “do not do X” instructionsDescribe the output you want; positive instructions outperform prohibitions.
Changing four things at once and declaring victoryChange one element, compare with the previous output, keep the better one.
Trusting an anti-hallucination technique as a guaranteeTreat 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.

Practice questions

Original questions written for this lesson, in the exam’s style. Answer first, then open the reasoning — every option is explained, including why the wrong ones are tempting.

  1. Question 1

    A policy officer attaches a 90-page consultation document and asks for the five main objections raised. The answer is well written, but two of the five objections do not appear anywhere in the document.

    What is the most effective next step?

    1. AAdd three examples of well-written objection summaries to the prompt.
    2. BAsk for exact quotes about objections first, then summarise only from those.
    3. CRephrase the request more precisely and specify a 500-word limit.
    4. DTell Claude to be accurate and not to make anything up in its answer.
    Show answer and reasoning
    1. AIncorrect. Examples teach style and structure, which were never the problem here — the content was not anchored to the source.
    2. BCorrect. Grounding the answer in quoted text before any summarising is the documented remedy for fabricated content in long documents.
    3. CIncorrect. Clearer phrasing and a word limit address shape and scope, not the invention of content that is not in the source.
    4. DIncorrect. A bare instruction to be accurate gives Claude no mechanism for grounding, unlike asking for quotes it must find.
  2. Question 2

    A team lead’s prompt asks Claude to summarise a project update, list risks, suggest mitigations, draft a client email and propose an agenda. The replies consistently cover the first three and skip the last two.

    What is the best diagnosis and fix?

    1. AThe model is too small for the task; switch to a more capable model.
    2. BThe request bundles five deliverables; split it into separate steps and check each.
    3. CThe prompt needs stronger wording, such as telling Claude it must complete all five.
    4. DThe conversation is too long; start a new chat with the same prompt.
    Show answer and reasoning
    1. AIncorrect. Model capability is not the constraint when the early parts of the same request are handled well.
    2. BCorrect. Dropped instructions typically mean too many requirements at once, and decomposition lets each output be produced and verified in turn.
    3. CIncorrect. Emphasis does not change the underlying problem that five deliverables are competing inside one response.
    4. DIncorrect. A fresh chat helps when quality degrades over a long thread, but the same overloaded prompt would fail the same way.
  3. Question 3

    An internal communications manager keeps getting updates in heavy bullet points when she wants flowing prose. She has already tried adding “do not use bullet points” to her prompt.

    Which two changes are most likely to help? (Select 2.)

    1. ADescribe the output positively — complete paragraphs of flowing prose.
    2. BWrite her own prompt in plain paragraphs rather than bullets.
    3. CAttach the source documents above her question.
    4. DAsk for step-by-step reasoning before the final answer.
    5. ERepeat the instruction three times in the prompt.
    Show answer and reasoning
    1. ACorrect. The documentation recommends telling Claude what to do rather than what to avoid when controlling output format.
    2. BCorrect. Output style tends to follow prompt style, so a prompt free of markdown pulls the response the same way.
    3. CIncorrect. Placing long inputs first helps with grounding and long-context performance, not with the formatting of the reply.
    4. DIncorrect. Exposing reasoning is a remedy for faulty logic and invented facts, not for the shape of the output.
    5. EIncorrect. Repetition of a prohibition does not address why the prohibition underperforms a positive description.

Sources

Drafted with AI assistance and checked against the sources above; expert review is in progress. Spotted an error? Tell us and it gets fixed, dated and listed on how this is written.