I tried adding Context7 Documentation MCP and got this

URL:https://mcp.context7.com/mcp Safety Scan: Passed

This MCP server can't be used by ChatGPT to search information because it doesn't implement our specification: search action not found https://platform.openai.com/docs/mcp#create-an-mcp-server

ref-tools-mcp is similar and does support openai's deep research spec