CSV group count

csv-group-count · version 1.0.0 · CSV & tables · free, no key needed

Count CSV rows by exact named-column tuples in first-seen order.

Use when you need to: csv group count · count csv rows by columns · csv group by.

Supported

• csv group count
• count csv rows by columns
• csv group by

Not supported

• sum other columns
• sort groups
• case fold
• numeric bins

Behavior

• The first CSV record is the header row.
• Duplicate and empty header names are rejected.
• group_columns is a non-empty unique list of exact header names.
• A group key is the JSON array of exact cell strings for those columns.
• No trimming, case folding, type coercion, or other normalization is performed.
• Groups appear in first-seen order.
• Output CSV headers are the group_columns followed by count.
• count is a base-10 integer string of the matching data-row count.
• A group column named count is rejected as a header collision.
• An empty document is invalid when group_columns is supplied.
• A header-only document yields the group headers plus count and zero data rows.

Input

• csv (string, required): max length 256000
• group_columns (array of string, required): min items 1; max items 32; each min length 1

Output

• csv (string, required)
• rows_in (integer, required)
• groups_out (integer, required)

Limits

• max input bytes: 256000
• max data rows: 5000
• max columns: 256
• max header name bytes: 256
• max group columns: 32

Example

Request input:

{
  "csv": "k,v\na,1\na,2\nb,1\n",
  "group_columns": [
    "k"
  ]
}

Response:

{
  "result": {
    "csv": "k,count\na,2\nb,1\n",
    "rows_in": 3,
    "groups_out": 2
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "csv-group-count",
  "version": "1.0.0",
  "input": {
    "csv": "k,v\na,1\na,2\nb,1\n",
    "group_columns": [
      "k"
    ]
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/csv-group-count/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"csv":"k,v\na,1\na,2\nb,1\n","group_columns":["k"]}'

The machine-readable contract is at /v1/tools/csv-group-count/versions/1.0.0.

CLI

node cli.mjs run csv-group-count 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• CSV dedupe: Remove duplicate CSV data rows while preserving the first occurrence.
• CSV sort: Stably sort CSV rows by exact named string columns.
• CSV row diff: Compare two CSV documents with identical headers by unique key tuples and report added, removed, and changed rows.
• CSV split column: Split one CSV column on an exact separator into uniquely named columns.
• CSV transpose: Transpose a CSV matrix including the header row, then re-validate headers.
• CSV add row number: Prepend a 1-based row_number column of canonical integer strings.