Ask HN: What's a standard way for apps to request text completion as a service?

If I'm writing a new lightweight application that requires LLM-based text completion to power a feature, is there a standard way to request the user's operating system to provide a completion?

For instance, imagine I'm writing a small TUI that allows you to browse jsonl files, and want to create a feature to enable natural language parsing. Is there an emerging standard for an implementation agnostic, "Translate this natural query to jq {natlang-query}: response here: "?

If we don't have this yet, what would it take to get this built and broadly available?