Deceptively small stories??

For sometime now I have got the feedback from developers, that the stories I write look small but have loads of work to be actually done and they get under estimated during the Iteration Planning Meeting. Now when I asked for a way in which I could make the story look as big as it is, I was given the idea of putting tasks in the story.

I have used this method for sometime now and I find myself writing things like:

TASK 1: When the user clicks "OK" an empty Word template should be uploaded to the server and then the same file should be opened for editing

whereas I would have generally written:

Clicking "OK" should open MS Word with an empty template so that the user can edit the contents.

While this puts implementation into the story and makes the story really bulky, it seems to really help the devs and may even be of help to a technically inclined client or the client's IT department which is going to take over the maintenance.

I think distributed agile makes us take many such deviations from the pure form of agile ideas we have read about. Most of these are justifiable in terms of the trade-off between concepts like "minimum documentation" and "transparency / knowledge sharing". After all isn't agile about doing whatever it takes to quickly deliver value to the customer??