Build a Universal App workflow that calls a third-party API or custom model endpoint through a server-side function. Use for API keys, webhooks, Azure OpenAI-compatible endpoints, payment, messaging, or any provider credential that must stay out of the browser.
Install
npx skills add microsoft/rayfin --skill external-api-workflowsnpx skills add microsoft/rayfin --skill external-api-workflows -a claude-code -gnpx skills add microsoft/rayfin --skill external-api-workflows -a codex -ggemini skills install https://github.com/microsoft/rayfin.git --path samples/universal-app/template/.agents/skills/external-api-workflowsgh skill install microsoft/rayfin external-api-workflowsgit clone --depth 1 https://github.com/microsoft/rayfin /tmp/microsoft__rayfin
mkdir -p ~/.claude/skills ~/.agents/skills
cp -R /tmp/microsoft__rayfin/samples/universal-app/template/.agents/skills/external-api-workflows ~/.claude/skills/external-api-workflows # Claude Code
cp -R /tmp/microsoft__rayfin/samples/universal-app/template/.agents/skills/external-api-workflows ~/.agents/skills/external-api-workflows # Codex, Cursor, Gemini CLI, Copilot, OpenCode