Types are a conversation with the next reader

I used to add types the way people add comments: after the code already knew what it was doing. That produces string and any in the places that actually hurt.

The useful types are the ones that name a decision. A status union. A result type that cannot be both data and an error. A function that refuses a partial object because the UI cannot render one.

If a type only repeats the variable name, delete it. If a type makes a future change fail in the compiler instead of in production, keep it.