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ArneVG's avatar
ArneVG
Copper Contributor
Apr 23, 2026

Failed to add tool to agent - Preview Feature Required?

Hi,

We’ve recently run into an issue where we’re no longer able to add tools to our Foundry agent. This was previously working without problems in our development environment, but now every attempt results in the following error:

“Failed to add tool to agent Request failed with status code 403.”

After inspecting the request in the browser’s developer console, we noticed an additional message:

"This operation requires the following opt-in preview feature(s): AgentEndpoints=V1Preview. Include the 'Foundry-Features: AgentEndpoints=V1Preview' header in your request."

 

How can we opt in for this foundry preview feature? and when was this change introduced?
We are unsure if the issue is related the the preview feature missing, or some other forbidden issue.

 

Any help would be very much appreciated.

Kind regards,

Arne

azure ai foundry

1 Reply

  • Surya_Narayana's avatar
    Surya_Narayana
    MCT
    Apr 25, 2026

    hi ArneVG​ The 403 combined with the AgentEndpoints=V1Preview message does suggest this is likely related to a preview feature requirement rather than a normal permissions issue.

    It looks like Microsoft may have recently moved some Foundry agent tool functionality behind an opt-in preview flag/API header. In many cases, these preview features are:

    Region/environment dependent

    Subscription/tenant gated

    Gradually rolled out

    If you’re using SDK/API calls, the request may now require the header:

    Foundry-Features: AgentEndpoints=V1Preview

    If this is happening through the portal/UI, then the backend service itself may not yet be enabled for your tenant/environment.

    I’d recommend:

    Checking the latest Azure AI Foundry preview documentation/release notes

    Verifying the environment/region supports the preview

    Opening a Microsoft support ticket, since 403 can also indicate the feature is not enabled server-side for your tenant

    The behavior does sound like a recent backend/platform change rather than something wrong in your implementation.