Last reviewed
Correct answer: C. Web search, which answers factual queries from live content
Explanation
The principle — the three capabilities differ by the shape of the question, not by how much you care about the answer.
Why the key is correct — Anthropic describes web search as best for straightforward factual queries answerable in one or two tool calls, giving checking the weather and retrieving recent news headlines as examples. A single published figure from yesterday is exactly that shape, and every response includes citations so you can confirm it.
Why the others are wrong — research is documented for comprehensive gathering requiring five or more tool calls over one to three minutes, which is disproportionate here. Extended thinking is for complex reasoning that does not need recent information, and no amount of reasoning yields a number the model never saw. And a plain chat cannot help, because the model's own knowledge does not extend forward on its own.
Remember this — one fact, one lookup. Save research for questions that need synthesis.
Sources — Anthropic's guidance on when to use each capability.
Sources
“Web search is best for straightforward, factual queries that can be answered with one or two tool calls”
“Research is optimal for comprehensive information gathering requiring five or more tool calls over 1-3 minutes, creating in-depth reports by synthesizing information from multiple sources.”
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