Auto generate index.d.ts, type definitions, from a typescript module

If I have a TypeScript module saved as my-function.ts as follows :

export function myFunction (param: number): number { return param }

This will be compiled to JavaScript in whichever way and loose its type definitions. I am then able to create a index.d.ts file which declare this module's definitions, but this seems a bit tedious to redefine/redeclare the definitions.

Are there ways to generate the type definitions automatically from the my-function.ts file to a index.d.ts file?

via dieheld