Similar to https://forum.plantuml.net/14763/how-can-add-the-description-explanation-to-the-json-diagram where i suggested a workaround of embedding the json inside a deployment diagram label.
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A work-around to JSON diagrams not supporting "title" is to embed the JSON diagram inside a deployment diagram. The label shape provides a nice container with minimal extra visual baggage.Lazily copying the OP's example from the above comments: