Hey there, does anyone know of a script to writes the size to the description. Not sure that can still be done in bridge

Define size… Pixels, Inches, CM etc.

This script writes the dimensions in pixels and the resolution:

/*
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);
      }
   }
}

Writing metadata to the description field is easy. Below is a sample script for editing description, you can skip the dialog window and just do it directly. Get the dimensions using the following:

var fileW = myFile.core.quickMetadata.width;
var fileH = myFile.core.quickMetadata.height;

#target bridge
if(BridgeTalk.appName == 'bridge'){
    var descCmd = MenuElement.create('command', 'Edit Description...', 'after Thumbnail/Open', this.menuID); //add to Contextual menu
    }

descCmd.onSelect = function(){
    descMain();
    }

descMain = function(){
    try{
        var descThumbs = app.document.selections; //get selected thumbnails
        if(!descThumbs.length) return; //nothing selected
        var descr = '';
        if(!descThumbs[0].hasMetadata) return; //no metadata
        var descMeta = descThumbs[0].synchronousMetadata;
        var descXMP = new XMPMeta(descMeta.serialize());
        if(descXMP.doesPropertyExist(XMPConst.NS_DC, 'description')){
            descr = descMeta.read(XMPConst.NS_DC, 'description');
            descr = descr.toString();
            }
        else{
            descr = '';
            }
        descWindow = new Window ('palette', 'Edit Description', undefined);
        descPanel = descWindow.add('panel', undefined, '');
        descPanel.orientation = 'column';
        descPanel.alignChildren = ['left', 'top'];
        descPanel.lbl1 = descPanel.add('statictext', undefined, 'Description:');
        descPanel.lbl1.graphics.font = 'palette-bold';
        descPanel.txt1 = descPanel.add('edittext {justify:"left"}', undefined, '');
        descPanel.txt1.preferredSize = [350, 80];
        descPanel.txt1.text = descr;
        descPanel.grp1 = descPanel.add('group', undefined, '');
        descPanel.grp1.preferredSize = [350, 50];
        descPanel.grp1.orientation = 'row';
        descPanel.grp1.alignment = ['fill', 'fill'];
        descPanel.grp1.margins = [30, 20, 0, 0];
        descPanel.grp1.button1 = descPanel.grp1.add('button', undefined, 'Cancel', {name: 'cancel'});
        descPanel.grp1.button2 = descPanel.grp1.add('button', undefined, 'Apply Changes', {name: 'ok'});
        descPanel.grp1.button2.enabled = false;

        descPanel.txt1.onChanging = function(){
            descPanel.grp1.button2.enabled = true;
            }

        descPanel.grp1.button1.onClick = function(){
            descWindow.close();
            }

        descPanel.grp1.button2.onClick = function(){
            descr = descPanel.txt1.text;
            descWindow.close();
            for(var a in descThumbs){ //loop through thumbs
                if(!descThumbs[a].container){
                    try{
                        descMeta = descThumbs[a].synchronousMetadata;
                        descXMP = new XMPMeta(descMeta.serialize());
                        descXMP.deleteProperty(XMPConst.NS_DC, 'description');
                        descXMP.setLocalizedText(XMPConst.NS_DC, 'description', null, 'x-default', descr);
                        var descUpdatedPacket = descXMP.serialize(XMPConst.SERIALIZE_OMIT_PACKET_WRAPPER | XMPConst.SERIALIZE_USE_COMPACT_FORMAT);
                        descThumbs[a].metadata = new Metadata(descUpdatedPacket); //write to file
                        }
                    catch(e){
                        Window.alert(e + e.line);
                        }
                    }
                }
            }
        descWindow.layout.layout(true);
        descWindow.show();
        descPanel.txt1.active = true;
        }
    catch(e){
        Window.alert(e + e.line);
        }
    }