MCP Server Card

What it checks

The extension looks for a document describing a Model Context Protocol (MCP) server at these paths on the site’s origin, in order, and stops at the first one that answers:

1. /.well-known/mcp.json
2. /.well-known/mcp/server-card.json
3. /.well-known/mcp/server.json
4. /.well-known/mcp

A path counts when it returns a successful response with a non-empty body that is JSON: either the Content-Type mentions json, or the body starts with { or [. That rules out an HTML page served with a 200 for a missing path. The extension does not validate the fields inside the document.

If none of those paths answers, the extension follows a pointer the site publishes to an MCP server hosted elsewhere, for example on a developer subdomain. It only follows a pointer the site itself declares: an entry in its agent catalog (/.well-known/ard.json or /.well-known/ai-catalog.json), or, with emerging checks enabled, a DNS-AID record. It never guesses a hostname, it does not follow redirects from the declared address, and it never requests an address on your local network unless the site being audited is on it too. The result names the host the descriptor was found on.

Results

Status	When
Pass	One of the paths returns a JSON document
Pass	A host the site declares serves one
N/A	None of the paths returns a JSON document

N/A is not charged against the site. Most sites do not run an MCP server.

How to fix

If you offer an MCP server, publish a JSON descriptor for it at /.well-known/mcp.json or /.well-known/mcp/server-card.json, served with Content-Type: application/json. It should at least name the server and say where to connect:

{
  "name": "Example MCP server",
  "description": "Search and manage orders.",
  "url": "https://example.com/mcp"
}

If you do not offer one, there is nothing to do.

Related: Agent Skills and WebMCP.

Support by agent and browser

Announced means the vendor’s own docs or announcement say so. Published is the date on the vendor’s own page, where it has one. Checked is the last time our weekly research found that page still saying so.

No agent or browser has announced anything about this yet.

No evidence yet27

• ChatGPT
• Claude
• Gemini
• Perplexity
• Copilot
• Meta AI
• ChatGPT Atlas
• Comet
• Dia
• Gemini in Chrome
• Edge Copilot Mode
• Claude Code
• Cursor
• Codex
• GitHub Copilot
• Windsurf
• CCBot
• Applebot
• Amazonbot
• Bytespider
• Cohere
• Mistral
• DuckAssist
• Chrome
• Edge
• Firefox
• Safari

Names and marks belong to their owners and are used only to identify products. None of these vendors is affiliated with Sitebulb. Spotted something out of date? Send a correction.

Adoption on the top 100 sites

4%

4 of 91 measured sites implement it

Scanned 23 Oct 2026 with the Sitebulb Labs extension, against the Tranco list (tranco-56Z8N). 9 sites couldn’t be measured (bot challenge or timeout) and are left out of the share.

Sites implementing it4

1. #2 cloudflare.com
2. #32 github.com
3. #68 zoom.com (via zoom.us)
4. #106 sentry.io

Overview

3/9

Speculative

Specified, but little evidence anything uses it yet.

How this rating is worked out3 of 9 points

Factor	Points	Why
Vendor support	0 / 3	0 vendors supporting, 0 partly or planned
Top-100 adoption	1 / 3	4% of measured sites
Spec maturity	2 / 3	Standards-track draft

8 or more points is Established, 5 to 7 is Gaining traction, 2 to 4 is Speculative and under 2 is Stalled. A feature is also Stalled when more vendors have said no than yes. Read the spec.

Community insights

No community insights for this feature yet.

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