{
 "acronym": "MCP Apps",
 "adoption": {
  "by": null,
  "level": "observed",
  "probe_run": null
 },
 "aliases": [
  "ext-apps",
  "Model Context Protocol UI Extension"
 ],
 "analog": "An iframe-embedded widget returned by a web API, rendered inline by the calling app",
 "collisions": [
  "MCP-UI (a separately-branded client SDK that implements this spec)"
 ],
 "discovery": {
  "mechanism": "A tool's definition declares a ui:// resource; the host fetches it via the standard MCP resources/read call after a tool call, rather than via a separate well-known path",
  "path": "ui://<resource-id> (declared per-tool, not a fixed site-wide path)"
 },
 "dispute": null,
 "evidence": [
  {
   "claim": "Canonical repo github.com/modelcontextprotocol/ext-apps (Apache-2.0 license, 2.8k stars, 666 commits, latest commit 2026-08-12): 'MCP Apps extend the Model Context Protocol by letting tools declare UI resources' via a 4-step flow (tool definition, tool call, host renders in a sandboxed iframe, bidirectional communication via notifications/tool calls). Spec file at specification/2026-01-26/apps.mdx. Supported clients listed in the repo's badges/table include ChatGPT, Claude, and VS Code, each linking to first-party docs for building MCP Apps in that client.",
   "date": "2026-09-05",
   "label": "VERIFIED",
   "url": "https://github.com/modelcontextprotocol/ext-apps"
  },
  {
   "claim": "MCP-UI (github.com/MCP-UI-Org/mcp-ui) describes itself as 'an SDK implementing the MCP Apps standard for UI over MCP,' offering a client (@mcp-ui/client) that can render via the MCP Apps AppRenderer or via a legacy UIResourceRenderer for pre-standard MCP-UI hosts — evidence that MCP Apps formalized and superseded an earlier, informally-specified MCP-UI proposal from mid-2025.",
   "date": "2026-09-05",
   "label": "VERIFIED",
   "url": "https://github.com/MCP-UI-Org/mcp-ui"
  }
 ],
 "form": "endpoint",
 "governance": "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",
 "group": null,
 "history": [
  {
   "date": "2026-09-06",
   "note": "new record: verified against github.com/modelcontextprotocol/ext-apps, its dated spec file, and github.com/MCP-UI-Org/mcp-ui; found via search for other agent-rendered-UI specs during A2UI/AG-UI verification"
  }
 ],
 "id": "mcp-apps",
 "implementation": "multi-implementation",
 "last_verified": "2026-09-06",
 "name": "MCP Apps",
 "native_status": "Active extension to MCP; own repo describes it as extending 'the Model Context Protocol by letting tools declare UI resources'",
 "origin": {
  "date": "2026-01-26",
  "org": "Model Context Protocol project (Anthropic-originated, now under the same governance umbrella as core MCP)"
 },
 "part_of": null,
 "parties": [
  "agent-human"
 ],
 "phase": "candidate",
 "probe": {
  "method": "POST",
  "on_absent": "Server exposes ordinary MCP tools with text/structured-data results only; no interactive UI capability",
  "parse": "Tool definition metadata includes a ui:// resource reference (or _meta.ui.resourceUri); a follow-up resources/read on that URI returns a resource with mimeType text/html (optionally ;profile=mcp-app)",
  "path": "{mcp-endpoint} — call tools/list then tools/call on a known MCP server, per JSON-RPC"
 },
 "question": "How does an MCP tool deliver an interactive UI (chart, form, dashboard) that renders inline in a chat client?",
 "scope": "general",
 "spec_url": "https://github.com/modelcontextprotocol/ext-apps/blob/main/specification/2026-01-26/apps.mdx",
 "step": "present",
 "summary_md": "MCP Apps is an extension to the Model Context Protocol (MCP) that lets an MCP server's tools declare an interactive UI — a chart, form, dashboard, or design canvas — that a compliant chat client renders inline, in the conversation, rather than as plain text or structured JSON. A tool definition declares a `ui://` resource containing bundled HTML/JavaScript; when the LLM calls the tool, the host fetches that resource over the ordinary MCP `resources/read` call and displays it in a sandboxed iframe; a bidirectional channel then lets the host push tool data into the UI via notifications and lets the UI call other MCP tools through the host [1]. It solves the specific gap that 'MCP tools return text and structured data... but not... an interactive UI' [1], and it explicitly targets the same problem A2UI and AG-UI's generative-UI feature address, but scoped to MCP-native tool calls rather than a general-purpose agent-to-frontend event stream.\n\nIt does not define a new transport (it rides on ordinary MCP JSON-RPC), does not specify how a host discovers that a server supports it beyond ordinary MCP capability negotiation and per-tool `ui://` metadata, and does not address payment, identity, or non-MCP agent frameworks.\n\nCurrent state (as of 2026-09-05): the canonical repository is github.com/modelcontextprotocol/ext-apps, Apache-2.0 licensed, with a dated spec file at `specification/2026-01-26/apps.mdx` and a companion blog post on blog.modelcontextprotocol.io dated 2026-01-26 announcing it. The repo shows sustained activity (666 commits, latest merge 2026-08-12, 2.8k stars) and ships an official npm package (`@modelcontextprotocol/ext-apps`) plus a React binding and a server-helpers package. The repo's own README lists ChatGPT, Claude, and VS Code as supported clients, each with first-party integration docs, which is stronger implementation evidence than a single reference build [1]. A separate, earlier community project, MCP-UI (github.com/idosal/mcp-ui, now under the MCP-UI-Org), predates MCP Apps and originally proposed its own `ui://`/`ui-app://` resource convention starting around April 2025; it has since repositioned itself explicitly as 'an SDK implementing the MCP Apps standard,' with a legacy rendering path kept only for pre-standard MCP-UI hosts [2]. The ext-apps repo itself credits MCP-UI's client as 'a fully-featured MCP Apps framework used by a few hosts,' alongside the possibility that a client rolls its own implementation.\n\nWhat is disputed or unknown: this is a new record on agenticweb.wiki, not previously tracked, so there is no prior baseline to compare against. Its governance track is marked 'community' here because the ext-apps repo, while living under the modelcontextprotocol GitHub org, is an 'ext-' (extension) project and it is not yet confirmed whether it has been formally folded into the same Agentic AI Foundation/Linux Foundation governance this site's core `mcp` record cites — that should be checked against MCP's own governance documents on a future pass. No independent, counted adoption figure exists; the evidence here is qualitative (named supported clients, repo activity), not a probe-based census.",
 "track": "community",
 "version": {
  "date": "2026-01-26",
  "label": "npm package @modelcontextprotocol/ext-apps, spec dated 2026-01-26"
 },
 "url": "https://agenticweb.wiki/protocols/mcp-apps/",
 "category": "present",
 "type": "protocol"
}