Best way to share typescript definitions in a npm workspace

I have setup a monorepo using npm’s workspaces feature. There are right now two separate apps within the repo that both consume an API that lives in a separate repo. I’d really like to share the API’s typescript definitions.

To this end I set up a “common” library in the monorepo for shared code. For code itself this works fine. The JavaScript and its Typescript definitions can be imported into the two other projects in the monorepo. However the API definitions have no corresponding code, they’re just d.ts files. The build process ignores them entirely.

All I can think of is to write class definitions in the common library and export those to the other apps, but of course that’s not quite as clean as a using d.ts file.

Any other things I could try?