I'm trying to use Microsoft Flow and the Send an HTTP request to SharePoint action to deploy an SPFx application customizer to a modern team site.

I'm able to use the /_api/Site/UserCustomActions endpoint to list existing custom actions but keep getting errors when I try to create new using REST

Site address: https://contoso.sharepoint.com/sites/a-modern-team-site

Method: POST

Uri: /_api/Site/UserCustomActions


  • Accept application/json; odata=verbose
  • Content-Type application/json; odata=verbose


    '__metadata': { 'type': 'SP.UserCustomAction' },

Here's the error I keep getting. I have tried various encoding of the client side properties, omitted it, but no results. I have tried different variations of the http headers, both with odata=verbose and odata=nometadata. I keep getting the same error, but can't find anything explaining the error.

  "status": 400,
  "message": "An unexpected 'PrimitiveValue' node was found when reading from the JSON reader. A 'StartObject' node was expected.\r\nclientRequestId: 43c303e3-4722-4b5e-a5b5-5fbcc686ec50\r\nserviceRequestId: 1b1e6c9e-a0a1-5000-f082-74dd369cc50f",
  "source": "https://contoso.sharepoint.com/sites/a-modern-team-site/_api/Site/UserCustomActions",
  "errors": [


  • Thanks for posting though, saved me a lot of trial and error (the UserCustomActionCollection does not support the PUT method and I was wondering how to create actions then, now that I knew a simple POST works for you I tried it for myself and indeed it does :)
    – frevd
    Oct 14, 2018 at 21:12

1 Answer 1


I finally figured out what was wrong. The "Rights" property doesn't take a string like "ManageWeb" but is an object with High and Low properties.

I had to either remove the property or define the High and Low permission mask bits.

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