The maximum character for the title is 80 character and description is 300 character.
Use images that are at least 1200 x 630 pixels for the best display on high-resolution devices. At the minimum, you should use images that are 600 x 315 pixels to display link page posts with larger images.
If your image is smaller than 600 x 315 px, it will still display in the link page post, but the size will be much smaller.
Minimum Image Size
The minimum image size is 200 x 200 pixels. If you try to use an image smaller than this you will see an error in the URL Debugger.