tl;dr

Access Azure blob metadata in two steps: obtain a SAS URI, then make an HTTP request — HEAD to read or PUT to write. Accessing index tags isn’t straightforward; secure a SAS URI that permits tag manipulation elsewhere, then return to complete the task.

Scrumptious if not tedious details

Azure blobs are fast and cost efficient. Just ask any Power Platform admin trying to shoehorn storing 250,000 email attachments in Dataverse — mostly self-proclaiming signatures — into the annual budget, and have a box of tissues ready.

To help manage storage classification and search, blobs have very useful additional features like metadata and index tags. See Manage properties and metadata for a blob with .NET and Manage and find Azure Blob data with blob index tags. Short version: metadata are for additional blob properties (e.g. image EXIF data), while tags are effective classification and search mechanism across containers and blobs.

Metadata

Power Automate can easily manipulate blobs using Azure Blob Storage Connector. One cannot be faulted for thinking a method called “Get Blob Metadata (V2)” would return, uhm, metadata. It does return something that looks like a warped version of blob properties but does not contain the actual metadata.

Luckily, metadata is just an HTTP request away: Get Blob Metadata (REST API) – Azure Storage. All we need is SAS key which we can get using the connector: Create SAS URI by path (V2). Request write privilege when creating SAS key and the metadata can be updated as well.

HEAD request returns metadata with the prefix x-ms-meta- as part of the headers block.

{
    "statusCode": 200,
    "headers": {
        "ETag": "\"0x8DC3CABED4F27DF\"",
        "Server": "Windows-Azure-Blob/1.0,Microsoft-HTTPAPI/2.0",
        "x-ms-request-id": "dfd94108-b01e-0011-620c-832521000000",
        "x-ms-version": "2018-03-28",
        "x-ms-meta-width": "670",
        "x-ms-meta-height": "370",
        "Date": "Sun, 31 Mar 2024 01:38:42 GMT",
        "Content-Length": "0",
        "Last-Modified": "Tue, 05 Mar 2024 00:33:49 GMT"
    }
}

Tags

Tags are a little bit more complicated because permissions for tags are governed separately and connector does accommodate them. You can get appropriate permissions baked into the SAS URI using Azure portal, just make sure to add Tags permissions.

Generated SAS URI can then be used in Power Automate to access index tags. The only difference from the metadata manipulation besides SAS URI and comp query parameter is that we append new tag instead of overwriting (involves a bit of xml manipulation; yes, tags use xml structure).

The result:

Would you rather poke the steps yourself? Download the unmanaged solution which includes a sample flow and connection reference.