MCP Apps

The server ships four browser-based views that MCP clients supporting the MCP Apps protocol can render inline or in fullscreen. They are delivered as a single HTML resource at ui://vault/app.html and use visibility="app" so they appear only in supporting clients.

Views

Context Card

Displays a note dossier for the note currently in focus. Includes:

• Backlinks — other notes that link to this note
• Outlinks — notes this document links to, with existence check
• Similar notes — semantically similar documents (requires embeddings)
• Tags — frontmatter tag values
• Folder peers — other notes in the same folder
• Modification time — last modified timestamp

Click any linked note to navigate to its context card.

Graph Explorer

Interactive force-directed link graph of the vault, powered by vis-network. Two modes:

• Neighborhood — shows a note and its direct connections (configurable depth)
• Hubs — shows the most-linked notes in the vault and their connections

Click a node to view that note's context card. Toggle semantic similarity edges when embeddings are available.

Vault Browser

Searchable, filterable file tree for navigating the vault without issuing tool calls. Features:

• Expandable folder tree
• Real-time search filtering
• Click a note to preview it in the Note tab

Note Preview

Full-width markdown preview with:

• Rendered markdown (via marked.js, sanitized with DOMPurify)
• Frontmatter table
• Send to Claude button — sends the note content to the LLM conversation
• Navigation to Context Card or Graph Explorer for the same note

Tools

Two primary tools are exposed to MCP clients:

Tool	Description
browse_vault	Opens the vault explorer SPA; optionally focuses a specific note and view. Returns a text summary for non-Apps clients.
show_context	Opens the Context Card for a given note path.

browse_vault accepts an optional path parameter to focus on a specific note, and a view parameter (context, graph, browse, or note). show_context requires a path parameter.

Six additional app-only tools (prefixed with _vault_) handle data fetching for the SPA views. These are hidden from the LLM and only callable from within the app itself.

Configuration

Variable	Default	Description
MARKDOWN_VAULT_MCP_BASE_URL	—	Public base URL of the server. Required for auto-computing the app domain.
MARKDOWN_VAULT_MCP_APP_DOMAIN	(auto)	Override the Claude app domain used for iframe sandboxing. Auto-computed from BASE_URL when not set.

Domain auto-computation

When APP_DOMAIN is not set, the server computes it from BASE_URL and HTTP_PATH:

1. Concatenate: mcp_url = f"{BASE_URL}{HTTP_PATH}"
2. SHA-256 hash the URL and take the first 32 hex characters
3. Result: {hash_prefix}.claudemcpcontent.com

Override APP_DOMAIN if your deployment is behind a proxy that changes the apparent hostname.

Architecture

The SPA is a self-contained HTML file with all dependencies vendored at build time (no runtime CDN requests):

Library	Purpose
vis-network	Force-directed graph rendering
marked.js	Markdown to HTML rendering
DOMPurify	XSS sanitization
@modelcontextprotocol/ext-apps	MCP Apps lifecycle, messaging, and theming

The app integrates with the host client via the ext-apps SDK:

• app.callServerTool() — calls app-only tools to fetch data
• app.sendMessage() — sends note content to the LLM conversation
• app.updateModelContext() — keeps the LLM aware of which note the user is viewing
• app.requestDisplayMode() — requests fullscreen or inline display
• Theme sync — automatically adapts to the host's light/dark theme and CSS variables

Client support

MCP Apps views require a client that supports the MCP Apps protocol. Currently supported by Claude on claude.ai. Clients without Apps support receive a text-only fallback from browse_vault and show_context.