Be explicit: state format, length, and no extras
Give the bot a clear, explicit instruction about format and scope, such as 'Answer only the question in one sentence, with no preamble, caveats or follow-up.' Specific constraints, a defined output format and an example usually work better than a vague request to be brief.
Answered from what it already knows
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Chatbots tend to add context, caveats and offers of further help because they are trained to be helpful and thorough. Clear, specific instructions about what to leave out, what format to use and how long to be generally reduce this. Positive framing ('reply with just the answer') plus a format spec and an example is usually more reliable than a negative-only instruction. Adherence is not perfect, so for strict needs you can use structured output modes or post-process the response. Results vary by model and tool.
- State the constraint directly, e.g. 'Respond with only the answer. No introduction, explanation, or closing remarks.'
- Specify the format and length, such as one word, one sentence, a number, or JSON only.
- Put the instruction in the system prompt or at the start of the conversation so it persists.
- Show an example of the desired output (few-shot) so the bot copies the style.
- Models may still add extras sometimes, so you can restate the rule or ask it to revise: 'Repeat, answer only.'