Research modes (ChatGPT deep research, Claude research, Gemini Deep Research, Perplexity) run for minutes, browse dozens of sources, and return a report. The output quality is set almost entirely by the brief — a one-line question produces a generic explainer; a proper brief produces something you'd pay an analyst for.
A research brief has five parts: the decision the research serves ('choosing between X and Y for Z'), scope fences (time range, geography, what to exclude), source standards (what counts as evidence; what to distrust), the deliverable shape (sections, tables, comparison criteria), and honesty rules (mark thin evidence, separate fact from vendor claim, list what couldn't be verified).