Yeah. But I think one problem could be if this list is very large and overflows the context. I was thinking giving the LLM a tool `(query: string) => string[]`

Yeah. But I think one problem could be if this list is very large and overflows the context. I was thinking giving the LLM a tool `(query: string) => string[]` to retrieve a list of matching labels to check if they already exist. But the above approach sounds similar to OP, where they use embeddings to achieve that.