Data / PromptFreeStarterRun on ChatGPT, Claude and Gemini on 14 Nov 2026
Check a spreadsheet export before you trust it
Goes through your file column by column and lists the blanks, duplicates and odd values that would bend your answer, before you analyse anything.
Use it when
You have an export from a CRM, shop or survey tool and someone wants an answer from it today.
You will need
- The file, uploaded, or its headers and first 50 rows pasted in
- Where the data came from
- The question you want the data to answer
The prompt
ROLE
You are a careful data analyst who checks the data before anyone draws a conclusion.
CONTEXT
File: [UPLOAD THE FILE, OR PASTE THE HEADERS AND FIRST 50 ROWS]
Source: [WHERE IT CAME FROM, FOR EXAMPLE A CRM EXPORT]
The question: [WHAT YOU WANT TO FIND OUT]
TASK
Check this data before I use it. Do not answer my question yet.
STEPS
1. If you cannot open the file or see the headers, tell me and stop.
2. Tell me how many rows and columns you read.
3. For each column, say what it seems to hold, how many cells are blank, and anything odd.
4. Look for duplicate rows, dates in mixed formats, numbers stored as text, total rows mixed in with the data, and values far outside the rest.
5. Say whether the data can answer my question, and what is missing.
RULES
- Report only what you found in the file. If you saw only part of it, say which part.
- When you are guessing what a column means, mark it [CHECK].
- Do not clean or change anything yet.
OUTPUT
A table with columns: column, what it holds, blanks, problems. Under it, the problems ranked by how much they would change the answer. Then yes, no or partly: can this data answer my question?
Example output, shortened
Rows read: 2,410. Columns: 9.
order_date. Dates. 12 blank. Two formats mixed (03/04/2026 and 2026-04-03), so March and April may be swapped. [CHECK]
Problem 1. 38 rows appear twice, with the same order number and amount.
Sample for an invented online shop's order export. Your output will differ.
Make it better
- Write a step-by-step plan to fix the top three problems that I can follow in Excel or Google Sheets.
- Which of these problems would I miss if I only made a chart? Show how each one would bend the result.
Watch out for
With a large file, some tools read only the first rows and report on those as if they were the whole file. Compare the row count the model gives you with the row count in your spreadsheet.
How we test
On 14 Nov 2026, a script filled in this prompt with an invented work example and ran it on ChatGPT (GPT-6.1 Terra), Claude Sonnet 5.5 and Gemini 4 Hydrogen. A separate AI model then checked each answer against what this page says the prompt does and what to watch out for. The label only appears when most answers pass. No person tried it by hand, and your answers will differ with your own input.
Next step / Prompt chainMembers
From a messy export to a one-page report, in four prompts
Takes a raw spreadsheet export through checking, a cleaning plan, the analysis and a one-page report, with every number traceable to the file.
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