Marks & Signatures for ChatGPT
com.marksandsignatures/marksandsignatures-com
Identify marks on pottery, silver, jewelry and glass, and look up their makers.
client:ChatGPT
transport:streamable-http
tools:5
Install Marks & Signatures in ChatGPT
Settings → Connectors → Advanced → Developer mode
https://marksandsignatures.com/api/mcpCustom connectors are a paid-plan feature and take a remote URL only. ChatGPT cannot run a packaged server locally. ChatGPT docs