Form compare

form-compare · version 1.0.0 · Forms · free, no key needed

Compare two filled form snapshots and return compact field and answer changes.

Use when you need to: compare filled forms · form snapshot diff.

Supported

• compare filled forms
• form snapshot diff

Not supported

• fuzzy matching
• html extraction
• pdf or ocr
• silent answer merge

Behavior

• Each snapshot carries its own fields and answers. Fields are diffed by exact id.
• Answers use the shared precedence only when both fields exist, the types are equal, and choice or multi sets contain the same strings.
• If the type or choice set differs, a non-missing answer is incomparable, even when a side is invalid for its own type. Choice order alone does not.
• A one-sided field adds or removes an answer only for null or a valid value. An invalid value stays invalid and is not added or removed.
• Both nulls compare equal and are unchanged. That is comparison equality, not validation. multi order-only changes are not value changes.
• Top-level counts repeat the nested field and answer counts. Nothing is truncated; over-budget output is rejected.

Input

• left (object, required)
• right (object, required)

Output

• fields (object, required)
• answers (object, required)
• counts (object, required)

Limits

• max input bytes: 262144
• max output bytes: 262144
• max input depth: 16
• max input nodes: 20000
• max fields: 100
• max choices: 50
• max respondents: 100
• max id bytes: 128
• max label bytes: 256
• max choice bytes: 128
• max answer string bytes: 4096
• max answer depth: 6
• max answer nodes: 50
• max changes: 500
• max mapping: 100

Example

Request input:

{
  "left": {
    "fields": [
      {
        "id": "email",
        "label": "Email",
        "type": "string",
        "required": true
      },
      {
        "id": "name",
        "label": "Name",
        "type": "string",
        "required": true
      }
    ],
    "answers": {
      "email": "a@b.test",
      "name": "Ada"
    }
  },
  "right": {
    "fields": [
      {
        "id": "name",
        "label": "Full name",
        "type": "string",
        "required": true
      },
      {
        "id": "role",
        "label": "Role",
        "type": "choice",
        "required": true,
        "choices": [
          "admin",
          "member"
        ]
      }
    ],
    "answers": {
      "name": "Ada Lovelace",
      "role": "admin"
    }
  }
}

Response:

{
  "result": {
    "fields": {
      "added": [
        {
          "id": "role",
          "field": {
            "id": "role",
            "label": "Role",
            "type": "choice",
            "required": true,
            "choices": [
              "admin",
              "member"
            ]
          }
        }
      ],
      "removed": [
        {
          "id": "email",
          "field": {
            "id": "email",
            "label": "Email",
            "type": "string",
            "required": true
          }
        }
      ],
      "changed": [
        {
          "id": "name",
          "changes": [
            "label"
          ],
          "left": {
            "id": "name",
            "label": "Name",
            "type": "string",
            "required": true
          },
          "right": {
            "id": "name",
            "label": "Full name",
            "type": "string",
            "required": true
          }
        }
      ],
      "order_changed": false,
      "counts": {
        "added": 1,
        "removed": 1,
        "changed": 1,
        "unchanged": 0,
        "reordered": 0
      }
    },
    "answers": {
      "added": [
        {
          "id": "role",
          "presence": "value",
          "value": "admin"
        }
      ],
      "removed": [
        {
          "id": "email",
          "presence": "value",
          "value": "a@b.test"
        }
      ],
      "changed": [
        {
          "id": "name",
          "reason": "value",
          "left_presence": "value",
          "right_presence": "value",
          "left": "Ada",
          "right": "Ada Lovelace"
        }
      ],
      "invalid": [],
      "order_only": [],
      "incomparable": [],
      "unknown": [],
      "counts": {
        "added": 1,
        "removed": 1,
        "changed": 1,
        "invalid": 0,
        "order_only": 0,
        "incomparable": 0,
        "unknown": 0,
        "unchanged": 0,
        "fields": 3,
        "left_missing": 1,
        "left_null": 0,
        "left_empty": 0,
        "right_missing": 1,
        "right_null": 0,
        "right_empty": 0
      }
    },
    "counts": {
      "fields_added": 1,
      "fields_removed": 1,
      "fields_changed": 1,
      "fields_unchanged": 0,
      "fields_reordered": 0,
      "answers_added": 1,
      "answers_removed": 1,
      "answers_changed": 1,
      "answers_invalid": 0,
      "answers_order_only": 0,
      "answers_incomparable": 0,
      "answers_unknown": 0,
      "answers_unchanged": 0
    }
  }
}

How to call it

MCP

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

{
  "id": "form-compare",
  "version": "1.0.0",
  "input": {
    "left": {
      "fields": [
        {
          "id": "email",
          "label": "Email",
          "type": "string",
          "required": true
        },
        {
          "id": "name",
          "label": "Name",
          "type": "string",
          "required": true
        }
      ],
      "answers": {
        "email": "a@b.test",
        "name": "Ada"
      }
    },
    "right": {
      "fields": [
        {
          "id": "name",
          "label": "Full name",
          "type": "string",
          "required": true
        },
        {
          "id": "role",
          "label": "Role",
          "type": "choice",
          "required": true,
          "choices": [
            "admin",
            "member"
          ]
        }
      ],
      "answers": {
        "name": "Ada Lovelace",
        "role": "admin"
      }
    }
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/form-compare/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"left":{"fields":[{"id":"email","label":"Email","type":"string","required":true},{"id":"name","label":"Name","type":"string","required":true}],"answers":{"email":"a@b.test","name":"Ada"}},"right":{"fields":[{"id":"name","label":"Full name","type":"string","required":true},{"id":"role","label":"Role","type":"choice","required":true,"choices":["admin","member"]}],"answers":{"name":"Ada Lovelace","role":"admin"}}}'

The machine-readable contract is at /v1/tools/form-compare/versions/1.0.0.

CLI

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

Get the client at /clients/cli/.

Related tools

• Form answer diff: Diff two answer maps against one shared form definition.
• Form definition diff: Diff two form definitions by stable field id, including choice lists and field order.
• Form response diff: Reconcile two form response sets by exact respondent id.
• Form field map: Rename form fields with an explicit id map and reject collisions.
• Form response check: Report missing required answers, nulls, type failures, and choice failures.