Yes it is okay. The curing temperature for Kato Polyclay™ is as high as 300 degrees Fahrenheit and glass beads can more than withstand this temperature. The issue you may have, depending on how you place the beads into the clay, is that the beads will not stick to the clay.
Here are a few things to try to resolve this:
Place the beads into the clay so the clay comes out of the hole of the seed bead--this will anchor the bead to the clay and give you a greater chance at having the bead becoming part of your design.
Use a good quality paintbrush to apply a layer of Kato Polyclay clear medium liquid or a layer of Signature Series Poly Bonder™ onto the surface of the clay, put the bead into place, and then bake per the manufacturer's directions. The clear medium liquid or adhesive should act like a glue as well as leave a nice finish on your design.
If you bake the bead in place and remove it after baking, the bead can be glued back into place after the piece has cooled. The glue will leave a shiny spot on the clay so use care if you decide to go with this technique.
- Tammy Honaman, Author, Jewelry-Making Expert and Educator