MCP Apps vs Agent-User Interaction Protocol (AG-UI)
The map lists them as complementary: sites and agents commonly implement both.
| MCP Apps MCP Apps | Agent-User Interaction Protocol AG-UI | |
|---|---|---|
| Lifecycle step | 8 Present: Show a human the result | 8 Present: Show a human the result |
| Answers | How does an MCP tool deliver an interactive UI (chart, form, dashboard) that renders inline in a chat client? | How does an agent stream state, generative UI, messages, and tool activity into a user-facing application in real time? |
| Governed by | modelcontextprotocol GitHub org (ext-apps sub-project); same umbrella as core MCP, which is now stewarded by the Agentic AI Foundation / Linux Foundation per this site's existing 'mcp' record | AG-UI open-source project (github.com/ag-ui-protocol), originated and still primarily stewarded by CopilotKit; biweekly public working group |
| Status (issuer's words) | Active extension to MCP; own repo describes it as extending 'the Model Context Protocol by letting tools declare UI resources' | 1.0 released and frozen; JSON Schema published |
| Version | v2.0.3 (2026-09-25) | 1.0 (2026-09-18) |
| Form / transport | endpoint | endpoint |
| Found at | ui://<resource-id> (declared per-tool, not a fixed site-wide path) | No fixed well-known path; a client is coded against a known agent backend endpoint that emits an AG-UI-compatible event stream over an agreed transport (SSE, WebSockets, webhooks) |
| Implementation | multi-implementation | multi-implementation |
| Evidence | 4 verified | 4 verified, 2 reported |
| Primary use case | Render agent output as a user interface | Render agent output as a user interface |
| Last verified | 2026-10-23 (current) | 2026-10-23 (current) |
| Specification | https://github.com/modelcontextprotocol/ext-apps/blob/main/specification/2026-01-26/apps.mdx | https://docs.ag-ui.com/introduction |
When to use which
- Choose MCP Apps when your question is “How does an MCP tool deliver an interactive UI (chart, form, dashboard) that renders inline in a chat client?” and you accept its maturity: status "Active extension to MCP; own repo describes it as extending 'the Model Context Protocol by letting tools declare UI resources'", implementation multi-implementation.
- Choose Agent-User Interaction Protocol when your question is “How does an agent stream state, generative UI, messages, and tool activity into a user-facing application in real time?” and you accept its maturity: status "1.0 released and frozen; JSON Schema published", implementation multi-implementation.
Read the full articles
- MCP Apps: How does an MCP tool deliver an interactive UI (chart, form, dashboard) that renders inline in a chat client?
- Agent-User Interaction Protocol: How does an agent stream state, generative UI, messages, and tool activity into a user-facing application in real time?