{"command":{"effect":"write","timeoutSeconds":30,"inputSchema":{"type":"object","description":"**This endpoint creates a new custom field definition.**\n\nCustom field definitions are created with the given `name` and `field_type`. Although field names are stored in a case-sensitive manner, all field names must be case-insensitively unique. This means you may create a field named `CamelCase` or `camelcase`, but not both. Additionally, a Custom Field name cannot collide with any Reserved Field names. You should save the returned `id` value in order to update or delete the field at a later date. You can have up to 500 custom fields.\n\nThe custom field name should be created using only alphanumeric characters (A-Z and 0-9) and underscores (\\_). Custom fields can only begin with letters  A-Z or underscores (_). The field type can be date, text, or number fields. The field type is important for creating segments from your contact database.\n\n**Note: Creating a custom field that begins with a number will cause issues with sending in Marketing Campaigns.**","properties":{"body":{"type":"object","properties":{"name":{"type":"string","minLength":1,"maxLength":100},"field_type":{"allOf":[{"$ref":"#/definitions/FieldType"},{"type":"string"}]}},"required":["name","field_type"],"examples":[{"name":"custom_field_name","field_type":"Text"}]}},"required":[],"additionalProperties":false,"definitions":{"FieldType":{"type":"string","enum":["Text","Number","Date"]}}},"name":"Create Custom Field Definition","id":"sendgrid.mc_custom_fields.createfielddefinition","example":{},"maxRequests":1,"summary":false}}