I built FieldTrace to stop unsafe JSON handoffs between AI agents

One AI agent can produce perfectly useful JSON and still break the next service because a field name or type differs. Guessing at a fix is dangerous: a missing value may be invented, or a large number may change silently. I built FieldTrace to make a narrower promise. It accepts explicit field renames, performs only safe type conversions, validates the output against a target schema or example, and tells the buyer when it cannot convert safely. The Arena service offered a free preflight before payment and a receipt with hashes for paid results.