JSON pointer get

json-pointer-get · version 1.0.0 · JSON & JSONL · free, no key needed

Return the cloned JSON value at an RFC 6901 pointer.

Use when you need to: json pointer get · get json pointer · read json pointer.

Supported

• json pointer get
• get json pointer
• read json pointer

Not supported

• json patch
• create missing
• prototype walk
• fetch

Behavior

• Accept only JSON values: null, boolean, finite number, string, array, and plain objects.
• Reject NaN, Infinity, -Infinity, undefined, BigInt, functions, symbols, Date, Map, Set, RegExp, boxed primitives, Buffer, and sparse holes.
• Canonicalize -0 to 0.
• Objects may have null or Object.prototype; use own enumerable string keys only.
• Treat __proto__, constructor, and toString as ordinary own keys. Never mutate Object.prototype.
• Output objects must be Object.create(null). Deep-clone all returned JSON values.
• Bound walk: max depth 32, max nodes 10000, max UTF-8 JSON bytes 250KiB of the input document string if provided as text; when json is already a value, bound the walked node count and depth.
• pointer is RFC 6901. Empty pointer returns a clone of the whole value.
• Tokens: split on /, reject pointer not empty and not starting with /.
• ~0 decodes to ~ and ~1 to /. A ~ not followed by 0 or 1 is invalid.
• On objects, use Object.hasOwn only. Array tokens must be "0" or [1-9][0-9]* with no leading zeros. "-" is not an existing index.
• Missing path, out-of-range index, or indexing a primitive is invalid_input.

Input

• json (any JSON value, required)
• pointer (string, required): max length 1024

Output

• value (any JSON value, required)

Limits

• max json depth: 32
• max json nodes: 10000
• max pointer chars: 1024

Example

Request input:

{
  "json": {
    "a": [
      {
        "b": 1
      }
    ]
  },
  "pointer": "/a/0/b"
}

Response:

{
  "result": {
    "value": 1
  }
}

How to call it

MCP

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

{
  "id": "json-pointer-get",
  "version": "1.0.0",
  "input": {
    "json": {
      "a": [
        {
          "b": 1
        }
      ]
    },
    "pointer": "/a/0/b"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/json-pointer-get/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"json":{"a":[{"b":1}]},"pointer":"/a/0/b"}'

The machine-readable contract is at /v1/tools/json-pointer-get/versions/1.0.0.

CLI

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

Get the client at /clients/cli/.

Related tools

• JSON flatten: Flatten a JSON value into a null-prototype map keyed by RFC 6901 JSON Pointers.
• JSON pointer has: Return whether an RFC 6901 pointer exists as an own path.
• JSON pointer list: List RFC 6901 pointers to every reachable JSON node, root first.
• JSON unflatten: Reconstruct a JSON value from a map of RFC 6901 JSON Pointers to leaves.
• Array to JSONL: Serialize an array of JSON-safe values as JSON Lines text.
• JSON array anti join: Anti join two JSON arrays of objects on exact keys.