---
title: "POST /events/custom/2026-09/event-definitions/{eventName}/property"
method: POST
path: "/events/custom/2026-09/event-definitions/{eventName}/property"
tags: ["Advanced"]
---

# POST /events/custom/2026-09/event-definitions/{eventName}/property

`POST /events/custom/2026-09/event-definitions/{eventName}/property`

## Path parameters

- `eventName` string, required

## Request body

- ExternalBehavioralEventPropertyCreate
  - `description` string — A description of the property that will be shown as help text in HubSpot.
  - `label` string, required — Human readable label for the property. Used in HubSpot UI
  - `name` string — Internal property name, which must be used when referencing the property from the API
  - `options` OptionInput[] — A list of available options for the property if it is an enumeration. NOTE: This field is only applicable for enumerated properties.
    - `description` string — null
    - `displayOrder` integer, required
    - `hidden` boolean, required
    - `label` string, required — null
    - `value` string, required — null
  - `type` string, required — The data type of the property. Can be one of the following: [string, number, enumeration, datetime]

## Response `201`

successful operation

- Property — A HubSpot property
  - `archived` boolean — Whether the property is archived.
  - `archivedAt` string, date-time — The timestamp when the property was archived, in ISO 8601 format.
  - `calculated` boolean — Whether the property is a calculated field.
  - `calculationFormula` string — The formula used for calculated properties.
  - `createdAt` string, date-time — The timestamp when the property was created, in ISO 8601 format.
  - `createdUserId` string — The ID of the user who created the property.
  - `dataSensitivity` 'highly_sensitive' | 'non_sensitive' | 'sensitive' — Indicates the sensitivity level of the property, such as "non_sensitive", "sensitive", or "highly_sensitive".
  - `dateDisplayHint` 'absolute' | 'absolute_with_relative' | 'time_since' | 'time_until'
  - `description` string, required — A summary of the property's purpose.
  - `displayOrder` integer — The position of the item relative to others in the list.
  - `externalOptions` boolean — Applicable only for enumeration type properties. Should be set to true with a 'referencedObjectType' of 'OWNER'. Otherwise false.
  - `fieldType` string, required — Determines how the property will appear in HubSpot's UI or on a form. Learn more in the properties API guide.
  - `formField` boolean — Whether the property can appear on forms.
  - `groupName` string, required — The name of the group to which the property is assigned.
  - `hasUniqueValue` boolean — Whether the property is a unique identifier property.
  - `hidden` boolean — Whether or not the property will be hidden from the HubSpot UI. It's recommended that this be set to false for custom properties.
  - `hubspotDefined` boolean — A boolean value set to true for HubSpot default properties.
  - `label` string, required — The display label for the property.
  - `modificationMetadata` PropertyModificationMetadata
    - `archivable` boolean, required
    - `readOnlyDefinition` boolean, required
    - `readOnlyOptions` boolean
    - `readOnlyValue` boolean, required
  - `name` string, required — The internal name for the property.
  - `options` Option[], required — A list of valid options for the property. This field is required for enumerated properties.
    - `description` string — A description of the option.
    - `displayOrder` integer — The position of the item relative to others in the list.
    - `hidden` boolean, required — Whether the option is displayed in HubSpot's UI.
    - `label` string, required — A user-friendly label that identifies the option.
    - `value` string, required — The actual value of the option.
  - `referencedObjectType` string — Deprecated. Use externalOptionsReferenceType instead.
  - `sensitiveDataCategories` string[] — When sensitiveData is true, lists the type of sensitive data contained in the property (e.g., "HIPAA").
  - `showCurrencySymbol` boolean — Whether to show the currency symbol in HubSpot's UI.
  - `type` string, required — The data type of the property, such as string or number.
  - `updatedAt` string, date-time — The timestamp when the property was last updated, in ISO 8601 format.
  - `updatedUserId` string

## Other responses

- `default` — An error occurred.

---

[API](https://skmtc.net/hubspot/apis/events-send-event-completions.md) · [All operations](https://skmtc.net/hubspot/apis/events-send-event-completions/llms.txt) · [OpenAPI document](https://skmtc-service-staging.skmtc.workers.dev/v1/apis/hubspot/events-send-event-completions/revisions/95737eb425c2/schema)