Returns the available data dependencies for AI-powered columns so clients can build valid prompts and grounding context before creating the column. This endpoint solves data dependency discovery for AI workflows by listing which audience columns and knowledge sources can be used as context for the selected AI column type. Use this to discover valid context sources, validate that selected context is supported, and choose relevant data dependencies that improve AI-generated output quality. Response entries include data dependency identifiers, display names, data types, and whether the source comes from an audience column (COLUMN) or from a knowledge source (KNOWLEDGE_BASE). Returns 200 OK with the list of supported data dependencies for the requested tool. Returns 400 if tool is invalid or not supported for data dependency discovery. Returns 404 if no audience matches the provided audienceId.