postalref for ChatGPT

com.postalref/postalref

USPS package barcodes, service type codes and mailing terms, each cited to its USPS source.

client:ChatGPT transport:streamable-http tools:8

Install postalref in ChatGPT

Settings → Connectors → Advanced → Developer mode

https://postalref.com/mcp

Custom connectors are a paid-plan feature and take a remote URL only. ChatGPT cannot run a packaged server locally. ChatGPT docs