Knowing What Claude Struggles With Makes It Even Easier to Use
Claude is strong in understanding text, summarizing, supporting ideation, and assisting with code. However, there are situations where it can sound convincing while being wrong. Beginners are especially likely to trust answers as-is because they come back in natural Japanese, but in real work it’s important to separate what it’s good at from what it can’t do.
This article organizes Claude’s representative weaknesses—hallucinations, weakness with real-time information, calculation mistakes, the fact that it can’t generate images, and that it’s not assumed to have internet search—from a practical usage perspective. It also introduces prompt techniques to reduce the chance of failure.
1. The Biggest Thing to Watch Out For: Hallucinations
Hallucination is the phenomenon where it presents content that is not factual in a plausible way. It can happen not only with Claude but with many generative AI systems.
Common patterns of occurrence
- Inventing non-existent sources: fake paper titles, URLs, book names, legal statute numbers, etc.
- Over-filling vague questions: making confident claims through speculation even when the premises are missing
- Mixing up details in specialized fields: be especially careful with medicine, law, taxation, security, and similar areas
- Changing parts too much in long summaries: adding conclusions that aren’t in the original text
- Mixing misinformation when aligning items in comparison tables
Typical example
Bad request example:
“Create a list of the subsidy programs latest in 2025.”
Common issues that arise:
- Answering under the assumption that it knows the latest programs
- Mixing in nonexistent program names or conditions
- Ignoring regional differences and timing differencesParticularly dangerous is the behavior of filling in without saying “I don’t know”. Because the output is natural, it can be difficult to notice the error.
How to respond
- For content that requires factual verification, set the assumption to confirm with primary sources
- Specify to write “unknown” when something is unclear and make it explicit that anything is speculation
- When asking for sources, provide the materials or URLs you have at hand
- In summarization, specify that you will not add anything not present in the original text
Example of an improved prompt:
“Summarize using only the following materials as the basis.
Do not add anything that is not written in the materials.
For unclear points, explicitly state ‘Cannot be confirmed in the materials.’”
