Why MCP and ChatGPT Apps Use Double Iframes — Frédéric Barthelet, Alpic
MCP and ChatGPT Apps render interactive UI via a double-iframe mechanism using tool-call-triggered HTML views.
“Views are always rendered as a result of a tool call.”
Alpic CTO Frédéric Barthelet explains how MCP and ChatGPT Apps use a double-iframe architecture to embed interactive UI 'views' inside conversational agents, with views rendered as the result of tool calls and advertised ahead of time via tool-list calls. It matters because it details the emerging standard (OpenAI's app SDK and MCP's app extension) for adding rich UI surfaces to ChatGPT and Claude, a new acquisition channel for businesses.