dtcat
Skill1 starsChanged 59 days agoMITView on GitHub
View and analyze tabular data files (CSV, TSV, Parquet, Arrow/Feather, JSON, NDJSON, Excel) using dtcat. Use when the user asks to open, view, inspect, read, or analyze a data file in any of these formats, or when you encounter such a file that needs to be examined. Also use when converting between formats.
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The file
We split this skill into the rules it gives an agent
5 rules. About 0 are common, 0 are distinctive, and 5 are very specific to this project.
≈0
Common · estimate
Many files like this have a rule of this kind.
≈0
Distinctive · estimate
This author's own choices. Worth a look.
5
Very specific
Tied to their project's names, files or tools. Probably skip.
- Common
- Distinctive
- Very specific
- Very specific: line 106
Run dtcat <file> to see the overview (schema + sample data)
- Very specific: line 108
Use --describe for statistical analysis
- Very specific: line 109
Use --head/--tail to zoom into specific regions, --sample for random rows
- Very specific: line 110
Use --csv when you need to pipe data to other tools
- Very specific: line 111
Use --convert to transform between formats (e.g., CSV to Parquet)
≈ “Common” is an estimate: at least 1 in 5 of the 350,495 skill files we read have a rule of the same kind, not the same words. “Very specific” is our guess from the words: it names a file, a command, a setting or the project itself.
Files
dtcat — Tabular Data File Viewer
View and analyze tabular data files at the command line. Supports CSV, TSV, Parquet, Arrow/Feather, JSON, NDJSON, and Excel. Outputs structured, LLM-friendly markdown.
Quick Reference
# Auto-detect format and show overview
dtcat data.csv
dtcat data.parquet
dtcat data.arrow
dtcat data.json
dtcat report.xlsx
# Column names and types only
dtcat data.parquet --schema
# Summary statistics per column
dtcat data.csv --describe
# File metadata (size, format, shape, sheets)
dtcat report.xlsx --info
# View a specific sheet (Excel only)
dtcat report.xlsx --sheet Revenue
# First/last N rows
dtcat data.csv --head 10
dtcat data.csv --tail 10
# Show all rows (override adaptive limit)
dtcat data.csv --all
# Random sample of rows
dtcat huge.parquet --sample 20
dtcat huge.parquet --sample 50 --csv
# Raw CSV output for piping
dtcat data.parquet --csv
# Convert between formats
dtcat data.csv --convert parquet -o data.parquet
dtcat report.xlsx --sheet Revenue --convert csv -o revenue.csv
dtcat data.parquet --convert ndjson # text formats go to stdout
# Override format detection
dtcat data.txt --format csv
# Skip metadata rows above header
dtcat data.csv --skip 2Supported Formats
| Format | Extensions | Auto-detected |
| CSV | .csv | Yes (magic + extension) |
| TSV | .tsv, .tab | Yes |
| Parquet | .parquet, .pq | Yes (PAR1 magic) |
| Arrow/Feather | .arrow, .feather, .ipc | Yes (ARROW1 magic) |
| JSON | .json | Yes ([ prefix) |
| NDJSON | .ndjson, .jsonl | Yes ({ prefix) |
| Excel | .xlsx, .xls, .xlsb, .ods | Yes (PK/OLE magic) |
Detection priority: --format flag > magic bytes > file extension.
Default Behavior
- <=50 rows: shows all data
- >50 rows: shows first 25 + last 25 rows
- Excel, multiple sheets: lists all sheets with schemas (use
--sheetto pick one)
Flags
| Flag | Purpose |
--format <fmt> | Override format detection (csv, tsv, parquet, arrow, json, ndjson, excel) |
--sheet <name|index> | Select sheet by name or 0-based index (Excel only) |
--skip <n> | Skip first N rows before header |
--schema | Column names and types only |
--describe | Summary statistics (count, mean, std, min, max, median, unique) |
--head <n> | First N rows |
--tail <n> | Last N rows |
--all | Show all rows (override adaptive limit) |
--sample <n> | Randomly sample N rows |
--csv | Output as CSV instead of markdown |
--info | File metadata (size, format, shape, sheets) |
--convert <fmt> | Convert to format (csv, tsv, parquet, arrow, json, ndjson) |
-o <path> | Output file path (required for binary formats with --convert) |
Exit Codes
| Code | Meaning |
| 0 | Success |
| 1 | Runtime error (file not found, corrupt) |
| 2 | Invalid arguments |
Workflow
- Run
dtcat <file>to see the overview (schema + sample data) - For Excel multi-sheet files, pick a sheet with
--sheet - Use
--describefor statistical analysis - Use
--head/--tailto zoom into specific regions,--samplefor random rows - Use
--csvwhen you need to pipe data to other tools - Use
--convertto transform between formats (e.g., CSV to Parquet)
Mutual Exclusivity
--schema,--describe,--info,--csv,--convertare mutually exclusive with each other--sampleis mutually exclusive with--head,--tail,--all--convertis mutually exclusive with all display flags
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