JSONL validate

jsonl-validate · version 1.0.0 · JSON & JSONL · free, no key needed

Validate strict JSON Lines text and report the value count and UTF-8 byte length.

Use when you need to: jsonl validate · validate json lines · check jsonl document.

Supported

• jsonl validate
• validate json lines
• check jsonl document

Not supported

• JSONL comments
• concatenated JSON without newlines
• NDJSON with blank lines
• JSON schema validation
• return valid false
• read files

Behavior

• text is strict JSON Lines split on CRLF, CR, or LF.
• A trailing empty segment after a final newline is ignored; internal empty lines are rejected.
• A document that is empty or only a trailing newline has zero JSON values.
• At most 5000 lines are accepted.
• Each line is parsed with JSON.parse and must be a JSON-safe value: object, array, string, boolean, null, or safe integer.
• Non-finite numbers, non-integers, and integers outside Number.MAX_SAFE_INTEGER are rejected.
• On success the output is valid true, the JSON value count, and the UTF-8 byte length of text.
• Invalid JSONL throws; the tool never returns valid false.

Input

• text (string, required): max length 256000

Output

• valid (constant true, required)
• lines (integer, required): min 0; max 5000
• bytes (integer, required): min 0; max 256000

Limits

• max input bytes: 256000
• max lines: 5000

Example

Request input:

{
  "text": "{\"name\":\"Ada\",\"ok\":true}\n\"שלום\"\n0\nnull\n"
}

Response:

{
  "result": {
    "valid": true,
    "lines": 4,
    "bytes": 43
  }
}

How to call it

MCP

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

{
  "id": "jsonl-validate",
  "version": "1.0.0",
  "input": {
    "text": "{\"name\":\"Ada\",\"ok\":true}\n\"שלום\"\n0\nnull\n"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/jsonl-validate/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"text":"{\"name\":\"Ada\",\"ok\":true}\n\"שלום\"\n0\nnull\n"}'

The machine-readable contract is at /v1/tools/jsonl-validate/versions/1.0.0.

CLI

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

Get the client at /clients/cli/.

Related tools

• Array to JSONL: Serialize an array of JSON-safe values as JSON Lines text.
• JSON schema validate: Validate a JSON instance against ComputeFirst Schema 1.0.
• JSONL to array: Parse strict JSON Lines text into an array of JSON-safe values.
• JSON array anti join: Anti join two JSON arrays of objects on exact keys.
• JSON array concat: Concatenate multiple JSON arrays of objects into one.
• JSON array count: Count structural occurrences in a JSON array in first-seen order.