The user will quote this output in a council meeting, where someone is paid to disagree with them. A number they cannot defend is worse than no tool.
This is your responsibility while building, not a disclaimer to append.
Put a check inside the tool
- A control total that must reconcile. Sum of parts against the stated total; row count in against row count shown. When it does not match, display the discrepancy prominently instead of continuing quietly.
- Count everything. “328 von 340 Zeilen verarbeitet” — and make the 12 inspectable. Silent dropping is the most damaging failure mode here, because the result still looks complete.
- Show the input next to the output. A drill-down from the total to the underlying rows turns “trust me” into “look”.
- Make assumptions visible and editable. If the tool assumes a rate, a distance band, a year: show it as a field the user can change. A model that cannot be poked at is a slide, not a tool.
For anything derived from documents
Never produce a bare summary. Produce the finding in one sentence, then the points that matter, each with the place it came from — page, section, annex.
The citation is what makes the claim quotable and the check cheap. Without it the user has to believe you, and that is not a basis for a public statement.
State limits in the output
Where the tool is uncertain, the output says so — inline, next to the figure, not in a footer:
- “Vergleich nur für Ansätze, die in beiden Jahren vorkommen (312 von 340).”
- “Beträge gerundet, Summe aus ungerundeten Werten.”
- “Diese Datei enthält keine Textebene — die Auswertung wäre geraten.”
Refusing to produce a number is a valid output. Producing a confident wrong one is not.
What to tell the user to verify themselves
When you hand over the tool, name the two or three things only they can check: a total they know, a figure they computed by hand, whether something they expect to be present is missing.
A real case: a tool counted committee meetings from email exports and got it wrong — an entire committee was missing. It was caught only because the person using it kept their own records. The tool counted; the human knew. Say this plainly rather than implying the output is final.
Offer the counter-arguments
When the user asks whether the result is right, the more useful answer is the list of attacks on it: which assumption is unverified, which figure is sensitive to a definition, which question an opponent would ask first. In practice this is often worth more than the result itself.