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What is this?

Normally you type a choice element’s options into the Flow Builder. Dynamic options are loaded while the customer is using the flow instead — from a web address you control, or from open slots in a Google Calendar. This is how you build things like appointment booking, where the available times depend on the date a customer picks. You choose this per element in its settings, under Static / Dynamic source. It is available on Single choice, Multiple choice, Dropdown, Chips, and Navigation list. Date picker and Calendar have their own endpoint options for minimum and maximum dates, and Calendar for unavailable dates. [SCREENSHOT: flows-dynamic-endpoint — The Static / Dynamic source section of a Dropdown set to Dynamic from endpoint, showing the How the endpoint is called help, the Endpoint URL box, Depends on field, and the Preview Resolve button]
A flow that loads data from your server needs the flow endpoint and encryption key to be in place. Flows you create with Create Flow use your workspace’s endpoint automatically, and the Versions / Endpoint column on the Flows page shows whether it is set. Google Calendar options also need a connected Google account — see Google Calendar.

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What can I do here?

  • Load a choice element’s options from your own URL
  • Show available appointment slots from a Google Calendar
  • Make a date picker’s earliest or latest date follow today’s date or your own URL
  • Block specific calendar days from your own URL
  • Check what a source returns with Resolve before you save

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How to use it

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Switch an element to a dynamic source

1

Select the element

Click the choice element in the preview and scroll to Static / Dynamic source in its settings.
2

Choose Dynamic

Click Dynamic. A Source mode list appears with Dynamic from endpoint and Dynamic from Google Calendar. Click Static at any time to go back to typing options (Static options, or Navigation items for a Navigation list).
3

Fill in the source

Complete the settings for the mode you chose (below), click Resolve to try it, then Save the flow.

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Dynamic from endpoint

Choose Dynamic from endpoint and enter an Endpoint URL (for example https://api.example.com/flow/options). The panel How the endpoint is called explains how it works. In short:
  • The platform sends a GET request to your URL exactly as you wrote it.
  • If your options depend on an earlier answer, put the token custom.<field_name> in the URL where the value belongs, using the Field name of that answer. When the customer answers, the token is replaced with their value.
  • If the URL already has parameters such as an API key, they are kept.
Your URL must return JSON in the shape shown under Expected response:
Depends on field (optional) lets the options depend on a Date picker or Calendar earlier in the flow. Choose it, then use custom. followed by that field’s name in the URL — the panel tells you the exact token to use. Leave it on No dependency if the options don’t change. If the flow has no date field yet, the panel notes “Add a DatePicker field only if your endpoint needs the selected date to return values.” Under Preview, click Resolve to call the URL now. Resolved values lists up to ten returned options (an id and a title each), and a Dynamic data resolved message says how many values came back. “No values returned.” means the URL answered with nothing. A Resolve failed message shows why a call failed, and Dynamic source disabled means you haven’t turned Dynamic on for the element.

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Dynamic from Google Calendar

[SCREENSHOT: flows-dynamic-calendar — A Dropdown set to Dynamic from Google Calendar showing Google Calendar, Lookahead days, Depends on date field, Slot duration (min), Working start, and Working end] Choose Dynamic from Google Calendar to offer open time slots from one of your calendars. Settings: Click Resolve (under Preview values) to see the slots the calendar would offer.
This only shows open slots. It does not reserve the one the customer picks, so the next customer could be offered the same time. To block the slot, add a Google Calendar step after the flow in your automation to create the event.

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Dates from an endpoint

On Date picker and Calendar elements, Min Date and Max Date can each be Static (a fixed date) or Dynamic. For Dynamic, choose a Source mode:
  • Current date — “Uses current date at runtime.”
  • Endpoint — enter an Endpoint URL that returns a date, either "2026-04-20", { "date": "2026-04-20" }, or { "value": "2026-04-20" }.
For a Calendar, Unavailable Dates can also be Dynamic: enter an Endpoint URL that returns a list such as ["2026-04-20", "2026-04-21"] or { "dates": ["2026-04-20"] }.

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Keep the flow’s endpoint working

On the Flows page, the Versions / Endpoint column shows Endpoint: OK, Mismatch, or Missing for each flow. Click Update Endpoint on a row, or the link icon above the table to fix every flow at once. The key icon sends your encryption key to WhatsApp — see Flows.

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Troubleshooting / Technical Notes

  • Save says the endpoint URL is empty. You chose Dynamic from endpoint but left Endpoint URL blank. Fill it in, or switch the element back to Static.
  • Save says no calendar is selected. Choose a calendar under Google Calendar. If the list is empty, connect Google first.
  • Save says the date field is empty. Calendar time slots need a Depends on date field. Add a Date picker to the flow and select it.
  • Resolve fails or returns nothing. Check the URL in a browser, that it returns JSON in the shape above, and that any custom. token matches the exact Field name of the earlier answer.
  • Customers see old or no options. Make sure the endpoint is OK on the Flows page and that the flow was saved after you changed the source.
  • Calendar slots don’t match my hours. Check Working start, Working end, and Slot duration (min), and that the right calendar is selected.
Last modified on October 6, 2026