JSON unflatten

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

Reconstruct a JSON value from a map of RFC 6901 JSON Pointers to leaves.

Use when you need to: json unflatten · unflatten json pointers · reconstruct json from pointers.

Supported

json unflatten
unflatten json pointers
reconstruct json from pointers
expand json pointer map

Not supported

json pointer get
json pointer set
sparse arrays
read files
fetch urls

Behavior

Own keys of pointers are RFC 6901 JSON Pointers; values are leaves.
The empty pointer denotes the entire document and must be the only key.
A pointer cannot be both a leaf and a prefix of another pointer.
The same parent cannot be used as both an array and an object.
Array indexes are canonical decimal tokens forming a dense range 0..n-1.
Reconstructed object keys are in lexicographic UTF-16 order of unescaped names; arrays are in index order.
Prototype-like keys are ordinary own keys on null-prototype objects.
Leaf values are null, boolean, string, safe integer, or an empty object or array.

Input

pointers (object, required)

Output

value (any, required)

Limits

max pointers: 5000
max depth: 16
max output bytes: 1048576

Example

Request input:

{
  "pointers": {
    "/name": "Ada",
    "/tags/0": "math",
    "/tags/1": "writer",
    "/address/city": "London"
  }
}

Response:

{
  "result": {
    "value": {
      "address": {
        "city": "London"
      },
      "name": "Ada",
      "tags": [
        "math",
        "writer"
      ]
    }
  }
}

How to call it

MCP

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

{
  "id": "json-unflatten",
  "version": "1.0.0",
  "input": {
    "pointers": {
      "/name": "Ada",
      "/tags/0": "math",
      "/tags/1": "writer",
      "/address/city": "London"
    }
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/json-unflatten/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"pointers":{"/name":"Ada","/tags/0":"math","/tags/1":"writer","/address/city":"London"}}'

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

CLI

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

Get the client at /clients/cli/.

JSON flatten: Flatten a JSON value into a null-prototype map keyed by RFC 6901 JSON Pointers.
JSON pointer list: List RFC 6901 pointers to every reachable JSON node, root first.
JSON array drop keys: Remove specific keys from each object in a JSON array.
JSON array group count: Group an array of JSON objects by exact keys and return the count.
JSON array index by: Convert an array of objects into a single object indexed by a specific key.
JSON array project: Select specific keys from each object in a JSON array.