Script to add Image Size to Description field to include in Printing Marks

Be aware that Save for Web will strip this out unless you use the All Metadata option. I write product weight into this field using a script, but also write it into the Headline field of my master PSD files. I have a second script that pulls the Headline data and writes it back into Description. That way I don't have to manually reenter the weights on my finished JPEG files.

Adobe Bridge is better suited to such things than Photoshop IMHO.

As I don't normally script Bridge, this hack is a little rougher than I would like (PNG files are not supported).

/*
https://community.adobe.com/t5/photoshop-ecosystem-discussions/script-to-add-image-size-to-description-field-to-include-in-printing-marks/td-p/14597499
*/

#target bridge

///// NOTE: PNG files will return the incorrect dimension and resolution values, ignore them!

if (BridgeTalk.appName == "bridge") {
   FT = MenuElement.create("command", "Add Dimensions & Resolution to Description", "at the end of Tools");
}

FT.onSelect = function () {
   //var thumbs = app.document.selections;
   var thumbs = app.document.getSelection('jpg, jpeg, tif, tiff, psd, psb, webp'); // Don't include PNG!
   if (!thumbs.length) return;
   if (ExternalObject.AdobeXMPScript == undefined) ExternalObject.AdobeXMPScript = new ExternalObject("lib:AdobeXMPScript");
   for (var a in thumbs) {
      var selectedFile = thumbs[a].spec;
      ///// Not for PNG
      var theRes = thumbs[a].core.quickMetadata.xResolution;
      ///// Rounded to 1 decimal place
      var theWidth = (thumbs[a].core.quickMetadata.width / thumbs[a].core.quickMetadata.xResolution).toFixed (1);
      var theHeight = (thumbs[a].core.quickMetadata.height / thumbs[a].core.quickMetadata.xResolution).toFixed (1);
      var theDims = theWidth + "in x " + theHeight + "in @" + theRes + "ppi";
      /////
      var myXmpFile = new XMPFile(selectedFile.fsName, XMPConst.UNKNOWN, XMPConst.OPEN_FOR_UPDATE);
      var myXmp = myXmpFile.getXMP();
      var Desc = [];
      var count = myXmp.countArrayItems(XMPConst.NS_DC, "description");
      for (var i = 1; i <= count; i++) {
         Desc.push(myXmp.getArrayItem(XMPConst.NS_DC, "description", i));
      }
      myXmp.deleteProperty(XMPConst.NS_DC, "description");
      myXmp.appendArrayItem(XMPConst.NS_DC, "description", theDims, 0, XMPConst.ALIAS_TO_ALT_TEXT);
      myXmp.setQualifier(XMPConst.NS_DC, "description[1]", "http://www.w3.org/XML/1998/namespace", "lang", "x-default");
      if (myXmpFile.canPutXMP(myXmp)) {
         myXmpFile.putXMP(myXmp);
         myXmpFile.closeFile(XMPConst.CLOSE_UPDATE_SAFELY);
      }
   }
}

https://prepression.blogspot.com/2017/11/downloading-and-installing-adobe-scripts.html