# Create Custom Field

Creates a custom-field definition and returns its ID and email placeholder. The type cannot change later. multiValue defaults to one value per subscription; changing to one value per contact later deletes extra values and cannot be reversed. Stores no contact values.

## Input schema:

```json
{
  "type": "object",
  "properties": {
    "name": {
      "type": "string",
      "description": "Name of the field, which has to be unique within the account",
      "minLength": 1,
      "maxLength": 250
    },
    "type": {
      "type": "string",
      "description": "Data type of the field, which decides what can be stored in it and cannot be changed afterwards",
      "enum": [
        "field-single",
        "field-paragraph",
        "field-email",
        "field-number",
        "field-url",
        "field-date",
        "field-time",
        "field-datetime",
        "field-html",
        "field-decimal"
      ]
    },
    "description": {
      "type": [
        "null",
        "string"
      ],
      "description": "What the field holds, so a person or a model reading it later knows what to write into it",
      "default": null,
      "maxLength": 2000
    },
    "multiValue": {
      "type": [
        "null",
        "boolean"
      ],
      "description": "True: one value per subscription; false: one value overall; omit for true",
      "default": null
    },
    "accountId": {
      "type": [
        "null",
        "integer"
      ],
      "description": "User ID of the account; omit for the account the access token works in",
      "default": null,
      "minimum": 1
    }
  },
  "required": [
    "name",
    "type"
  ],
  "additionalProperties": false
}
```

## Output schema:

```json
{
  "type": "object",
  "required": [
    "accountId",
    "id",
    "name",
    "type",
    "multiValue",
    "placeholder",
    "apiFieldId",
    "category",
    "description",
    "metaLabels",
    "editUrl",
    "usedBy"
  ],
  "properties": {
    "accountId": {
      "type": "integer"
    },
    "id": {
      "type": "string"
    },
    "name": {
      "type": "string"
    },
    "type": {
      "type": "string"
    },
    "multiValue": {
      "type": "boolean"
    },
    "placeholder": {
      "type": "string"
    },
    "apiFieldId": {
      "type": "string"
    },
    "category": {
      "type": "string"
    },
    "description": {
      "type": "string"
    },
    "metaLabels": {
      "type": "array",
      "items": {
        "type": "string"
      }
    },
    "editUrl": {
      "type": "string"
    },
    "usedBy": {
      "type": "array",
      "items": {
        "type": "string"
      }
    }
  }
}
```