# Agentic standards, measured

Home > Standards

How many sites actually implement each agentic web standard. Every figure dated,
with the population it was measured against.

## Measured

- [WebMCP](https://knowngood.sh/standard/webmcp.md): 580 of 647 tested, 2026-08-31. WebMCP lets a page register tools an agent can call, in the page itself, rather than at a separate endpoint. The site declares what can be done and the agent calls it directly — the page becomes the API.
- [Markdown negotiation](https://knowngood.sh/standard/markdown.md): 10,877 of 14,351 tested, 2026-08-23. A site that answers Accept: text/markdown with actual markdown hands an agent the content without the navigation, scripts and layout it would otherwise have to strip. The same URL, a cleaner representation.
- [Model Context Protocol](https://knowngood.sh/standard/mcp.md): 6,026 of 8,817 tested, 2026-08-23. MCP is the protocol an agent uses to discover and call a server's tools. On the open web a site advertises one through a server card, and an agent connects to the endpoint the card names.
- [llms.txt](https://knowngood.sh/standard/llms-txt.md): 11,154 of 14,351 tested, 2026-08-23. A file at /llms.txt listing the pages a site considers worth reading, in markdown, as a curated entry point rather than a crawl.
- [API catalog](https://knowngood.sh/standard/openapi.md): 5,399 of 14,351 tested, 2026-08-23. A machine-readable catalogue of a site's APIs at a well-known location, so an agent can find the interface without reading the documentation. Usually an OpenAPI document, discovered through /.well-known/api-catalog.

## Observed

- **Link headers**: Capability and relation links delivered in the HTTP response header rather than the document body. We serve them.
- **ARD (Agentic Resource Discovery)**: A manifest at a well-known path listing the agentic resources a site offers. We serve one, at /.well-known/ard.json.
- **UCP (Universal Commerce Protocol)**: A discovery layer that advertises a site's commerce endpoints to an agent. We do not serve it.
- **Web Bot Auth**: Signed HTTP requests that let a site verify which bot is calling it. We do not serve it.
- **x402**: Agent-payable HTTP: a 402 response an agent can settle to obtain the resource. We do not serve it.
- **ACP · MPP · AP2**: Commerce protocols for agent-initiated purchase and payment. We do not serve them.
- **DNS-AID**: Agent discovery at the DNS layer, published as records rather than over HTTP. We do not serve it.

Rubric: https://knowngood.sh/benchmark