I've been using the kendo.all.d.ts TypeScript definitions file from the beginning. While its quality has increased significantly overtime, it continues to have a lot of errors and omissions. I understand the Kendo UI TS definitions file is generated from the Kendo UI documentation. So the quality of the TS definitions file is only ever going to be as good as the documentation. And that's where the errors and omissions come from. Not everything is documented or documented correctly. I think the best Kendo UI TS definitions file can only be created when the Kendo UI source code itself is migrated to TS. Now that TS version 1.0 has RTM'ed it is time to do this. Spend an entire release doing this if you have to. Who knows how many bugs TS may expose and help to fix.