CSV merge columns

csv-merge-columns · version 1.0.0 · CSV & tables · free, no key needed

Join named CSV columns with an exact separator into one column.

Use when you need to: csv merge columns · join csv columns with separator · combine csv columns into one.

Supported

• csv merge columns
• join csv columns with separator
• combine csv columns into one

Not supported

• skip empty parts
• trim cells before joining
• regex join
• infer target name
• 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 merged headers and zero data rows.
• columns names 2 to 16 unique existing headers exactly. separator is a literal string of at most 16 UTF-16 code units and may be empty.
• Each output cell is columns.map(c => cell[c]).join(separator) with no trimming, skipping of empties, case folding, or type coercion.
• Source columns are dropped. into is inserted at the original index of columns[0] after earlier source columns are removed. into may equal a source column name but must not equal a remaining non-source header.
• 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
• columns (array of string, required): min items 2; max items 16; each min length 1; each max length 256
• separator (string, required): max length 16
• into (string, required): min length 1; 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 merge columns: 2
• max merge columns: 16
• max separator chars: 16
• max output bytes: 256000

Example

Request input:

{
  "csv": "id,first,last\n1,Ada,Lovelace\n2,Grace,Hopper\n",
  "columns": [
    "first",
    "last"
  ],
  "separator": " ",
  "into": "name"
}

Response:

{
  "result": {
    "csv": "id,name\n1,Ada Lovelace\n2,Grace Hopper\n"
  }
}

How to call it

MCP

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

{
  "id": "csv-merge-columns",
  "version": "1.0.0",
  "input": {
    "csv": "id,first,last\n1,Ada,Lovelace\n2,Grace,Hopper\n",
    "columns": [
      "first",
      "last"
    ],
    "separator": " ",
    "into": "name"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/csv-merge-columns/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"csv":"id,first,last\n1,Ada,Lovelace\n2,Grace,Hopper\n","columns":["first","last"],"separator":" ","into":"name"}'

The machine-readable contract is at /v1/tools/csv-merge-columns/versions/1.0.0.

CLI

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

Get the client at /clients/cli/.

Related tools

• CSV split column: Split one CSV column on an exact separator into uniquely named columns.
• CSV fill defaults: Replace empty cells in named CSV columns with exact default strings.
• CSV anti join: Keep left CSV rows whose exact key tuples do not appear in the right document.
• CSV concat: Concatenate CSV documents that share identical headers, preserving document and row order.
• CSV dedupe: Remove duplicate CSV data rows while preserving the first occurrence.
• CSV drop columns: Drop named CSV columns and keep the remaining columns in original header order.