# CSV split column

`csv-split-column` · version 1.0.0 · CSV & tables · free, no key needed

Split one CSV column on an exact separator into uniquely named columns.

**Use when you need to: csv split column · split a csv column by exact separator · expand csv column into named columns.**

## Supported

- csv split column
- split a csv column by exact separator
- expand csv column into named columns

## Not supported

- regex split
- infer column names
- trim cells
- limit split parts without throwing
- fuzzy matching
- read files
- fetch urls

## Behavior

- The first CSV record is the header row. An empty document is rejected; a header-only document yields the replaced headers and zero data rows.
- column must name an existing header exactly. separator is a non-empty literal string of at most 16 UTF-16 code units, never a regular expression.
- Each data cell is split with String.prototype.split(separator). More parts than names.length is rejected; fewer parts are padded with empty strings on the right.
- names is 2 to 16 unique non-empty headers. A name may equal column (in-place replacement) but must not equal any other remaining header.
- The original column is replaced in place by names, in names order. No trimming, case folding, or type coercion is performed.
- The first output header name may not begin with U+FEFF because it is ambiguous with a CSV byte-order mark.

## Input

- `csv` (string, required): max length 256000
- `column` (string, required): min length 1; max length 256
- `separator` (string, required): min length 1; max length 16
- `names` (array of string, required): min items 2; max items 16; each min length 1; each max length 256

## Output

- `csv` (string, required)

## Limits

- max input bytes: 256000
- max data rows: 5000
- max columns: 256
- max header name bytes: 256
- min names: 2
- max names: 16
- max separator chars: 16
- max output bytes: 256000

## Example

Request input:

```json
{
  "csv": "city,name\nLondon,Ada Lovelace\nParis,Grace Hopper\n",
  "column": "name",
  "separator": " ",
  "names": [
    "first",
    "last"
  ]
}
```

Response:

```json
{
  "result": {
    "csv": "city,first,last\nLondon,Ada,Lovelace\nParis,Grace,Hopper\n"
  }
}
```

## How to call it

### MCP

Connect `https://computefirst.net/mcp` ([setup](/docs#connect)), then call `execute` with:

```json
{
  "id": "csv-split-column",
  "version": "1.0.0",
  "input": {
    "csv": "city,name\nLondon,Ada Lovelace\nParis,Grace Hopper\n",
    "column": "name",
    "separator": " ",
    "names": [
      "first",
      "last"
    ]
  }
}
```

### HTTP (no key)

```sh
curl -X POST https://computefirst.net/v1/tools/csv-split-column/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"csv":"city,name\nLondon,Ada Lovelace\nParis,Grace Hopper\n","column":"name","separator":" ","names":["first","last"]}'
```

The machine-readable contract is at [/v1/tools/csv-split-column/versions/1.0.0](/v1/tools/csv-split-column/versions/1.0.0).

### CLI

```sh
node cli.mjs run csv-split-column 1.0.0 --input input.json --base-url https://computefirst.net
```

Get the client at [/clients/cli/](/clients/cli/).

## Related tools

- [CSV dedupe](/tools/csv-dedupe): Remove duplicate CSV data rows while preserving the first occurrence.
- [CSV merge columns](/tools/csv-merge-columns): Join named CSV columns with an exact separator into one column.
- [CSV filter equals](/tools/csv-filter-equals): Keep CSV data rows whose named column equals an exact string.
- [CSV group count](/tools/csv-group-count): Count CSV rows by exact named-column tuples in first-seen order.
- [CSV scale integer column](/tools/csv-scale-integer-column): Multiply every data cell in a named CSV column by a canonical integer factor.
- [CSV schema check](/tools/csv-schema-check): Validate a CSV document against an ordered column list and per-column string constraints.