CSV concat

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

Concatenate CSV documents that share identical headers, preserving document and row order.

Use when you need to: csv concat · concatenate csv documents · append csv rows with matching headers.

Supported

• csv concat
• concatenate csv documents
• append csv rows with matching headers
• stack csv documents

Not supported

• union mismatched schemas
• reorder columns to match
• fuzzy header matching
• case-insensitive headers
• read files
• fetch urls

Behavior

• documents is an array of 2 to 20 CSV strings; each string is bounded by the CSV byte limit.
• The first document supplies the output headers; every later document must have the same header names in the same order.
• An empty document without a header row is rejected; a header-only document contributes zero data rows.
• Output data rows follow document order, then row order within each document. Cells are not trimmed, case-folded, or type-coerced.
• The combined data-row count must not exceed the CSV row limit.
• The first output header name may not begin with U+FEFF because it is ambiguous with a CSV byte-order mark.

Input

• documents (array of string, required): min items 2; max items 20; each max length 256000

Output

• csv (string, required)
• documents_in (integer, required)
• rows_out (integer, required)

Limits

• min documents: 2
• max documents: 20
• max input bytes: 256000
• max data rows: 5000
• max columns: 256
• max header name bytes: 256
• max output bytes: 256000

Example

Request input:

{
  "documents": [
    "id,name,note\n1,Ada,\"hello, world\"\n",
    "id,name,note\n2,Lin,later\n"
  ]
}

Response:

{
  "result": {
    "csv": "id,name,note\n1,Ada,\"hello, world\"\n2,Lin,later\n",
    "documents_in": 2,
    "rows_out": 2
  }
}

How to call it

MCP

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

{
  "id": "csv-concat",
  "version": "1.0.0",
  "input": {
    "documents": [
      "id,name,note\n1,Ada,\"hello, world\"\n",
      "id,name,note\n2,Lin,later\n"
    ]
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/csv-concat/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"documents":["id,name,note\n1,Ada,\"hello, world\"\n","id,name,note\n2,Lin,later\n"]}'

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

CLI

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

Get the client at /clients/cli/.

Related tools

• CSV add row number: Prepend a 1-based row_number column of canonical integer strings.
• CSV anti join: Keep left CSV rows whose exact key tuples do not appear in the right document.
• CSV dedupe: Remove duplicate CSV data rows while preserving the first occurrence.
• CSV fill defaults: Replace empty cells in named CSV columns with exact default strings.
• CSV group count: Count CSV rows by exact named-column tuples in first-seen order.
• CSV inner join: Inner join two CSV documents on exact named key columns.