thinkhard.SI

Prompt repository Data & spreadsheets

Find errors and anomalies in a dataset

You need duplicates, outliers and suspicious values flagged before you trust the numbers.

Registry no.
DAT-014
Collection
Data & spreadsheets
Laid out for
Any chat model
Score
10 out of 10
Blanks to fill
5
Added

Data & spreadsheetsAny chat

The prompt

Score 10 of 10, Excellent

Use it when You need duplicates, outliers and suspicious values flagged before you trust the numbers.

  • {{data}}
  • {{column_rules}}
  • {{data_source}}
  • {{intended_use}}
  • {{app_and_version}}
Full prompt and why it works
Prompt
The data (pasted below or attached):
"""
{{data}}
"""

What each column should contain (type, allowed values or range, which column should be unique, which must never be blank):
"""
{{column_rules}}
"""

Where the data came from: {{data_source}}
What I will use it for: {{intended_use}}
App I am working in: {{app_and_version}}

Task: Check this data for errors and anomalies before I use it for {{intended_use}}. I need to know whether the numbers can be trusted, so that problems are fixed at the source rather than discovered in the results. This is a check, not a cleanup: flag what looks wrong and leave every value as it is.

Check for:
- Duplicates: exact repeats, near-repeats that differ only in spaces, capitals or punctuation, and repeated values in the column that should be unique.
- Missing values in required columns, including blanks disguised as "N/A", "0", "-" or a single space.
- Invalid values: outside the allowed range or list, negative where that is impossible, dates in the future, end dates before start dates.
- Signs of import damage: default dates such as 1900-01-01 or 1970-01-01, dates showing as numbers, long IDs shown in scientific notation, codes that have lost their leading zeros, numbers stored as text.
- Inconsistencies: totals that do not equal their parts, mixed units or currencies in one column, the same thing spelled several ways.
- Outliers: values far outside the rest of their column. Say how you judged "far", for example more than three times the median. An outlier is a value to check, not proof of an error.
- Test or dummy records, such as "test" or "asdf" in a name field.

Format:
1. Summary: rows and columns checked, and whether the data looks safe to use as it is, in up to 3 sentences.
2. Issue log: a table with the columns Issue, Column, Rows affected (row numbers or IDs), Example values (copied exactly), Severity (stops the analysis, distorts results, or cosmetic), How to confirm.
3. Formulas or filters for {{app_and_version}} that find each type of issue in the full dataset, with one line on what each does.

Do not correct, delete or fill any value, and do not guess what an error should have been. If you could see only part of the data, say how many rows you checked. If a column's meaning is unclear, say so instead of judging its values. Keep the text outside the table under 300 words.

Variables

{{data}}
The dataset with its header row, pasted as text or CSV, or attach the file. Remove personal data you do not need checked.
{{column_rules}}
For each column: what it should hold, allowed values or range, and whether it must be unique or never blank.
{{data_source}}
Where the data came from, for example "a CRM export" or "a form merged from two spreadsheets".
{{intended_use}}
What you will use it for, for example "the quarterly sales report to the board".
{{app_and_version}}
Where you will check the full file, for example Excel for Microsoft 365, Google Sheets or Power Query.

Why it works

  • What to avoid. This is a check, not a cleanup: no value is changed, deleted or filled, and an outlier is treated as something to verify, not as an error.
  • What to make. Each check is spelled out, including the signs of import damage a quick scan misses, such as 1900-01-01 dates, IDs in scientific notation and lost leading zeros.
  • Format. An issue log with rows affected, exact example values and severity, plus formulas for the full file, turns the check into a list you can work through.

How to use it

  1. Press Fill in variables and type your details into each blank. What you type stays in this browser.
  2. Copy the filled prompt into the AI tool you already use, such as ChatGPT, Claude or Gemini, or open it in the Grader or the Prompt Tester here.
  3. Before you rely on it, try it on three or four real examples. The Prompt Tester runs them all at once and shows which ones go wrong.
Use it from code

Get this prompt as JSON from the free REST API, with your own text in the blanks, or let an AI assistant fetch it through the MCP server. No key.

curl -s https://thinkhard.si/api/v1/prompts/spot-data-errors-and-anomalies

With the MCP server added to Claude, ChatGPT, Cursor or VS Code, call get_prompt with {"prompt": "spot-data-errors-and-anomalies"}, or just ask for it by name.