LangChain Tool - NEAR Receipt Parser

Build a LangChain tool for receipt parser on NEAR.

THE VIRAL LOOP: LangChain agent needs receipt parser → Uses NEAR tool → Agent operates on NEAR

Deliverables:

1. LangChain BaseTool implementation
2. Async support
3. Error handling
4. Published to PyPI as langchain-near-receipt-parser
5. Listed on LangChain Hub

Success Metric: 30+ downloads