Be Specific — Goal, Context, Format
Tripmate's first system prompt was one line: "You are a helpful travel assistant." It chatted pleasantly, recommended flights Asha cannot afford, and answered in long paragraphs her app could not display. The model was not the problem. The prompt left almost everything to guesswork.
The rule
Say the goal, give the context, name the format — leave nothing to guess.
A prompt is the model's whole briefing. Four ingredients do most of the work:
- A specific goal — what counts as success. "Find train options" is vague; "find up to three trains that arrive before 10 am on the 16th" is testable.
- Relevant context — facts the model cannot know: the user's budget, their preferences, today's date, what the tools do, what the company's rules are.
- Precise terms — use the words of the field. "Sleeper class", "tatkal quota" or "PNR" point the model at exact meanings; "the cheap beds" does not.
- Length and format — how long, and in what shape: bullet points, a table, or JSON with named fields.
You are Tripmate, a train-travel assistant for users in India.
Today is 2026-10-12. The user's budget is ₹2,500 per person, one way.
Goal: suggest up to 3 trains that arrive before the user's deadline.
Prefer sleeper or 3A class. Never book without explicit confirmation.
Reply as a bullet list: train name, departure, arrival, class, fare.
Keep the whole reply under 80 words.Every line removes a guess. None of it is clever wording; it is simply information the model did not have. Notice too that the rules are stated positively where possible ("reply as a bullet list") rather than only as bans; telling the model what to do is easier to follow than a list of things to avoid.
The shortcut
Read your prompt as if you were a smart new colleague on their first day who knows nothing about this project. For each sentence of the task, ask: "Could they get this wrong without asking me a question?" Wherever the answer is yes, add a line.
Goal
New colleague: "Find it for when, arriving by when?" Add: arrive in Jaipur before 10 am on 16 October.
The trap is thinking longer is always better. Burying the goal under pages of loosely related text makes it harder to follow. Add what removes guesses; cut what does not.
Drills
Answer fast — trust the rule.
Which goal is the most specific?
Tripmate keeps suggesting trains over budget. What is the most likely missing ingredient?
Asha's app shows only short plain lists. What should the prompt add?
Why write "sleeper or 3A class" instead of "the cheap beds"?
Remember
- Say the goal, give the context, use precise terms, name the length and format.
- Shortcut: brief a smart new colleague — where could they go wrong without asking?
- Trap: padding the prompt with text that adds length but removes no guesses.