§5.2 · COMPARE · LAST REVIEWED SEPTEMBER 2026
MCP vs WebMCP: which one does your site need?
Same idea of tools for agents, two different places they run.
Agent Readiness Compare editors · Spec status checked September 2026
Answer
MCP connects an agent to a server that exposes tools, resources and prompts; it suits API-backed tasks from any agent. WebMCP lets a web page register tools that an agent in the browser calls inside the page, using the user's session; it suits in-page tasks. MCP has a versioned specification (latest revision 2026-07-28); WebMCP is a W3C Community Group proposal in active development. Many sites will start with MCP and add WebMCP for browser flows.
On this page
1.How do they differ?
| Attribute | MCP | WebMCP |
|---|---|---|
| Where tools run | On a server you operate | In the web page, in the user's browser |
| Who calls them | Any MCP client: assistants, IDEs, agents | An agent running in the browser on that page |
| Session and auth | Authorization flows you implement (OAuth for remote servers) | The user's existing page session |
| Discovery | The client is configured with the server URL | The page registers tools when it loads |
| Messages | JSON-RPC 2.0 | JavaScript API (document.modelContext in the current explainer) |
| Maturity | Versioned specification, revision 2026-07-28 | Community Group proposal, in active development |
| Best for | Account actions, data lookups, API tasks | Search, filters, forms and flows on the page itself |
2.When does a website need MCP?
When agents should act on your product outside the browser: look up an account, create a record, start a trial, fetch usage. Host it next to your API; Cloudflare and Vercel both document MCP hosting.
3.When does a website need WebMCP?
When the task lives on the page: filtering a catalogue, comparing plans in a pricing widget, filling a multi-step form. WebMCP lets the page hand the agent a tool instead of a UI to click through.
4.Can you use both?
Yes. They are complementary: MCP for API tasks from any agent, WebMCP for in-browser tasks on your pages. Test each with the tools on /tools: ora.ai's WebMCP audit scores page tools, and an MCP client can call tools/list on your server.
Frequently asked questions
Is WebMCP a version of MCP?
No. WebMCP borrows the idea of described tools, but it is a separate browser proposal from the W3C Web Machine Learning Community Group.
Which should I build first?
If you have an API and want agents to act on accounts, MCP. If your key tasks happen in page UI, such as a pricing configurator, consider WebMCP, keeping in mind it is still a proposal.
Source: modelcontextprotocol.io specification · github.com/webmachinelearning/webmcp · Reviewed Sep 2026