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Why deterministic

Ask a plain LLM what moon phase governed a date, or what was retrograde, and you get a confident guess — often different the next time you ask. GEOMETRY replaces the guess with a lookup: sky anchors computed offline with the standard Swiss Ephemeris stack, stored once on the date spine, returned identically on every call. Reproduce it yourself:
  1. Ask any chatbot: What was the moon phase on 1985-03-15, and which planets were retrograde that day?
  2. Then ask the same via MCP after connecting https://mcp.geometry.app/mcp
Caption: same question, same model — the only difference is the data layer. Demo / marketing surfaces use Tool 2 (get_card_for_birthdate) for this proof — not Tool 1.