A while back I asked if anyone had messed about with scripting paths in Photoshop. I got little response. Anyway I persevered with the hope of creating a circle. Just for kicks, you understand (I must get out more). Turns out there isn't much info out there on the subject only that it's not possible to create a true circle with bezier curves. I've had a look it into it and I've managed a circular approximation with paths.

// draw circular path
// use at your own risk
// Author: ghoulfool
// Thanks to G. Adam Stanislav for the kappa explanation
// Kappa Kappa Hey!

app.preferences.rulerUnits = Units.PIXELS;

// OPTIONALS
var radius = 150; // radius of the circle to be drawn
var circX = 160; // centre of circle X
var circY = 160; // centre of circle Y

//  create a document to work with
var docRef = app.documents.add("320px", "320px", 72, "Circle");

// call the source document
var srcDoc = app.activeDocument;

// create new layer
var layerRef = srcDoc.artLayers.add()
layerRef.name = "circle"
layerRef.blendMode = BlendMode.NORMAL

//draw circle
drawCircle(circX , circY, radius, "circle")

function drawCircle(X,Y,rad, pathName)
{
var K = (4 * (Math.sqrt(2) - 1) / 3)* rad

// define circle points
var C = new Array();
C = [X, Y - rad, X + rad, Y, X, Y + rad, X - rad, Y, X + K, Y - rad, X + rad, Y - K, X + rad, Y + K, X - K, Y + rad, X + K, Y + rad, X - rad, Y + K, X - rad, Y - K, X - K, Y - rad];

// create the array of PathPointInfo objects
var lineArray = new Array();
lineArray.push(new PathPointInfo());
lineArray[0].kind = PointKind.CORNERPOINT;

lineArray[0].anchor = new Array(C[0], C[1]); // A
lineArray[0].leftDirection =  [C[8], C[9]];
lineArray[0].rightDirection = lineArray[0].anchor;

lineArray.push(new PathPointInfo());
lineArray[1].kind = PointKind.CORNERPOINT;
lineArray[1].anchor = new Array(C[2], C[3]); // B

lineArray[1].leftDirection = [C[12], C[13]];
lineArray[1].rightDirection =  [C[10], C[11]];

lineArray.push(new PathPointInfo());
lineArray[2].kind = PointKind.CORNERPOINT;
lineArray[2].anchor = new Array(C[4], C[5]); // C

lineArray[2].leftDirection = [C[14], C[15]];
lineArray[2].rightDirection =  [C[16], C[17]];

lineArray.push(new PathPointInfo());
lineArray[3].kind = PointKind.CORNERPOINT;
lineArray[3].anchor = new Array(C[6], C[7]);    // D

lineArray[3].leftDirection = [C[20], C[21]];
lineArray[3].rightDirection =  [C[18], C[19]];

lineArray.push(new PathPointInfo());
lineArray[4].kind = PointKind.CORNERPOINT;
lineArray[4].anchor = new Array(C[0], C[1]); 

lineArray[4].leftDirection = lineArray[4].anchor; 
lineArray[4].rightDirection =  [C[22], C[23]];

// create a SubPathInfo object, which holds the line array in its entireSubPath property.
var lineSubPathArray = new Array();
lineSubPathArray.push(new SubPathInfo());
lineSubPathArray[0].operation = ShapeOperation.SHAPEXOR;
lineSubPathArray[0].closed = false;
lineSubPathArray[0].entireSubPath = lineArray;

//create the path item, passing subpath to add method
var myPathItem = docRef.pathItems.add(pathName, lineSubPathArray);

// set foreground colour to green
var fgColor = new SolidColor;
fgColor.rgb.hexValue="00ff80"  //green colour
foregroundColor = fgColor

//fill the path 
myPathItem.fillPath(fgColor,ColorBlendMode.NORMAL,100,false,0,true,true);

//deselect path
// =======================================================
var id630 = charIDToTypeID( "Dslc" );
var desc154 = new ActionDescriptor();
var id631 = charIDToTypeID( "null" );
var ref127 = new ActionReference();
var id632 = charIDToTypeID( "Path" );
ref127.putClass( id632 );
desc154.putReference( id631, ref127 );
executeAction( id630, desc154, DialogModes.NO );
}

This was my second attempt. The first was on a semi circle basis with two points - but the circles looked very oval. This is much better I feel.

Enjoy!