Your blog inside Claude Desktop or Cursor in 5 minutes: agentprose + MCP-B

agentprose turns your blog into read-only WebMCP tools: search, full posts as Markdown, sections, related posts and checked citations. MCP-B’s local relay carries those tools from a browser tab to a desktop MCP client. Put the two together and Claude Desktop, Cursor or Claude Code can search and quote your blog from the tab you have open, with no server code and no API keys.

your blog tab                                   your computer
┌──────────────────────────────┐   WebSocket   ┌────────────────────────┐  stdio  ┌──────────────────┐
│ agentprose  → content tools  │──localhost──▶ │ @mcp-b/webmcp-local-   │ ──────▶ │ Claude Desktop / │
│ MCP-B polyfill or global     │               │ relay (MCP server)     │         │ Cursor / Claude  │
│ relay embed.js               │               └────────────────────────┘         │ Code             │
└──────────────────────────────┘                                                 └──────────────────┘

What you need: Node.js 22 or later (the relay runs with npx), Chrome or Edge, and an MCP client.

1. Put the tools on the page

agentprose needs one script tag. MCP-B’s embed connects the tab to the relay:

<script src="https://cdn.jsdelivr.net/npm/agentprose@0/dist/agentprose.min.js" defer></script>
<script src="https://cdn.jsdelivr.net/npm/@mcp-b/webmcp-local-relay@6/dist/browser/embed.js" defer></script>

agentprose loads MCP-B’s WebMCP polyfill on its own in browsers that don’t have WebMCP yet (after the page has loaded, about 9 KB). If your site already uses @mcp-b/global, agentprose registers into it and loads nothing extra.

Version note. The built-in polyfill ships in agentprose 0.1.1 and later (agentprose@0 serves it); from 0.1.2 it carries an integrity hash (details). On agentprose 0.1.0, add MCP-B’s runtime in <head> first: <script src="https://cdn.jsdelivr.net/npm/@mcp-b/global@6/dist/index.iife.js"></script>. That combination was tested end to end too (see below).

Should every visitor load the embed? Usually not. The embed looks for a relay on localhost ports 9333–9348 from every visitor’s browser. On a public site, Chrome asks each visitor for permission to reach their local network, and visitors without a relay see failed connections in the console. Three ways to keep it to yourself:

A bookmarklet (no site change). Make a bookmark with this URL and click it on any page that runs agentprose:
```
javascript:void(document.head.appendChild(Object.assign(document.createElement('script'),{src:'https://cdn.jsdelivr.net/npm/@mcp-b/webmcp-local-relay@6/dist/browser/embed.js'})))
```
The embed picks up tools that are already registered. It works on any agentprose site once the built-in polyfill is released (or today, on sites that load @mcp-b/global). Sites with a strict Content Security Policy block bookmarklet scripts.
A switch on your own site, e.g. load the embed only when the URL has ?relay or you are signed in.
A local copy. Serve your site on localhost while you write. That is also where the relay needs no permission prompt.

2. Add the relay to your MCP client

The client starts the relay itself. --widget-origin limits it to your site; without it, any page you open can offer tools to the agent.

Claude Desktop: Settings → Developer → Edit Config, which opens claude_desktop_config.json (macOS ~/Library/Application Support/Claude/, Windows %APPDATA%\Claude\):

{
  "mcpServers": {
    "webmcp-local-relay": {
      "command": "npx",
      "args": ["-y", "@mcp-b/webmcp-local-relay@latest", "--widget-origin", "https://yourblog.example"]
    }
  }
}

Restart Claude Desktop.

Cursor: add the same mcpServers block to ~/.cursor/mcp.json (all projects) or .cursor/mcp.json (one project).

Claude Code:

claude mcp add webmcp-local-relay -- npx -y @mcp-b/webmcp-local-relay@latest --widget-origin https://yourblog.example

For a local copy of your site, use its origin instead, e.g. --widget-origin http://localhost:4000.

3. Open your blog and ask

Open a post on your blog in Chrome or Edge (or click the bookmarklet on it).
If Chrome asks whether the site may access devices on your local network, choose Allow. That is the tab connecting to the relay on your own computer.
Ask the agent:
- “List the connected WebMCP sources.” It calls the relay’s webmcp_list_sources and shows your tab.
- “What does my blog say about pricing? Quote it with links.” It calls search_posts, then get_post and get_citation.
- “Summarise the post I have open, section by section.” It calls get_current_article and get_section.

The relay lists agentprose’s tools under their own names (search_posts, get_post, get_current_article, get_section, get_table_of_contents, list_posts, list_taxonomies, get_related_posts, get_citation, get_site_info, plus get_subscribe_link when the site has a feed link). With two tabs offering the same tool names, the relay adds a short suffix (search_posts_ed93). Every tool is read-only.

What was tested, and what wasn’t

Tested on 2026-10-18 with examples/mcp-b-desktop/verify.mjs: the official MCP TypeScript SDK client launched @mcp-b/webmcp-local-relay@6.0.3 over stdio, which is what Claude Desktop and Cursor do with the config above. Headless Chromium 156 without native WebMCP opened the agentprose demo blog. Then the client listed the tools and called webmcp_list_sources, get_current_article, search_posts, get_post and get_citation through the relay.

Page	Origin	Result
agentprose (built-in polyfill) + embed	`http://localhost`	✅ 11 tools in the relay ~0.5 s after load; all calls answered
`@mcp-b/global` 6.0.3 + agentprose + embed	`http://localhost`	✅ same
agentprose only, embed added after load (the bookmarklet)	`http://localhost`	✅ same
agentprose 0.1.0 from jsDelivr + `@mcp-b/global` + embed (examples/mcp-b-desktop/index.html)	`http://localhost`	✅ 10 tools; all calls answered
any of the above	a public `https://` origin	⚠️ Chrome blocked the connection to `localhost` (Local Network Access) until it is allowed; with that check switched off, standing in for clicking Allow, ✅ all calls answered

Not tested: Claude Desktop, Cursor and Claude Code themselves (the test machine has none; the SDK client speaks the same stdio protocol), the permission prompt in a headed Chrome, Firefox and Safari, and Windows paths.

Troubleshooting

The agent sees only the four webmcp_* tools. The tab isn’t connected. Reload it after the client has started (the embed retries after 10, 20 and 30 s, then every two minutes). Check that --widget-origin matches the page’s origin exactly, and that you allowed local network access.
webmcp_list_sources shows the tab with 0 tools. The page has no WebMCP runtime. On agentprose 0.1.0, add @mcp-b/global or data-polyfill. On 0.1.1 and later, check that data-polyfill="off" isn’t set and that your CSP allows https://cdn.jsdelivr.net (or self-host the polyfill: data-polyfill="/js/webmcp-polyfill.js").
file:// pages don’t work. Serve the page over http://localhost, because WebMCP needs a real origin.
Tool names clash with another tab. Close the other tab, or give agentprose a prefix: data-prefix="blog_".