Reduce loop iterations

Fewer iterations means fewer calls means less cost and latency:

• Batching tools. "Fetch these N documents" in one call avoids N serial iterations. "Extract all columns for this document in one call" instead of one call per cell.
• Good tool design and descriptions so the model picks the right tool first time instead of fumbling through several.
• Cheap discovery tools (list/find) so the model targets what it needs instead of reading everything and iterating.