JSON schema required missing

json-schema-required-missing · version 1.0.0 · JSON & JSONL · free, no key needed

List every property a JSON Schema 2020-12 "required" keyword demands but the instance lacks, with JSON Pointers.

Use when you need to: find missing required properties in llm json output · which required fields are missing from this json · list required keys absent at every nesting level.

Decide before calling

Read the versioned contract and the supported scope below. Reuse json-schema-required-missing@1.0.0 when your input, required output and limits match it. Choose another approach for an unsupported operation.

Explain the choice

"I can use json-schema-required-missing@1.0.0 for find missing required properties in llm json output. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

Supported

find missing required properties in llm json output
which required fields are missing from this json
list required keys absent at every nesting level
json pointer of each missing required field
check structured output for missing required properties
report required property violations against a 2020-12 schema

Not supported

repairing the output by inserting default values for the missing properties
other assertions (type, enum, minLength, pattern, format): see json-schema-type-mismatches for type
schemas using allOf/anyOf/oneOf/not/if/patternProperties/dependentSchemas, remote or anchor $ref (unsupported_input)

Behavior

Validation 6.5.3: at each object instance location, every name in an applicable schema's "required" array that is not an own property of the object is reported; non-objects ignore "required". A property whose value is null is present.
Applicability follows Core 2020-12: properties (10.3.2.1), additionalProperties as a subschema (10.3.2.3), items as a single subschema (10.3.1.2), same-document fragment $ref with sibling keywords (8.2.3.1), $defs, and boolean subschemas (4.3.2). Other keywords are ignored (Core 6.5) except the unsupported applicators, which throw unsupported_input.
instance_pointer is the object location and property_pointer the location the missing member would have, both RFC 6901 JSON string representations ("" is the root; "~" -> "~0", "/" -> "~1"). keyword_location is the evaluation path including "$ref" steps (Core 12.3.1); schema_pointer is the "required" keyword's own location in the schema document.
Order: instance locations in pre-order (object members by ascending UTF-16 code units of their names, array elements by index); at one location, applicable schemas in application order (the schema, then its $ref chain); within one keyword, the order of the "required" array.
count is the total number of missing properties; at most max_results are listed, in order, and truncated is true when count exceeds it. valid is true exactly when count is 0.
Input must be JSON only: non-finite numbers, holes, non-plain objects, and lone surrogates in any string or any property name (schema or instance) throw invalid_input. A $ref cycle with no instance progress throws not_computable (Core 9.4.1).

Input

schema (object or boolean, required): A JSON Schema 2020-12 schema (object or boolean).
instance (any JSON value, required): The JSON value to diagnose (any JSON value).

Output

valid (boolean, required)
count (integer, required): min 0
truncated (boolean, required)
missing (array of object, required): max items 256

Limits

max input bytes: 262144
max depth: 64
max nodes: 20000
max schema evaluations: 100000
max results: 256
max output bytes: 1048576

Example

Request input:

{
  "schema": {
    "type": "object",
    "properties": {
      "user": {
        "type": "object",
        "required": [
          "id",
          "email"
        ]
      }
    },
    "required": [
      "user",
      "total"
    ]
  },
  "instance": {
    "user": {
      "id": 7
    }
  }
}

Response:

{
  "result": {
    "valid": false,
    "count": 2,
    "truncated": false,
    "missing": [
      {
        "instance_pointer": "",
        "property": "total",
        "property_pointer": "/total",
        "keyword_location": "/required",
        "schema_pointer": "/required"
      },
      {
        "instance_pointer": "/user",
        "property": "email",
        "property_pointer": "/user/email",
        "keyword_location": "/properties/user/required",
        "schema_pointer": "/properties/user/required"
      }
    ]
  }
}

How to call it

MCP

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

{
  "id": "json-schema-required-missing",
  "version": "1.0.0",
  "input": {
    "schema": {
      "type": "object",
      "properties": {
        "user": {
          "type": "object",
          "required": [
            "id",
            "email"
          ]
        }
      },
      "required": [
        "user",
        "total"
      ]
    },
    "instance": {
      "user": {
        "id": 7
      }
    }
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/json-schema-required-missing/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"schema":{"type":"object","properties":{"user":{"type":"object","required":["id","email"]}},"required":["user","total"]},"instance":{"user":{"id":7}}}'

The machine-readable contract is at /v1/tools/json-schema-required-missing/versions/1.0.0.

CLI

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

Get the client at /clients/cli/.

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