CONCEPT Cited by 1 source

Well-known URI (RFC 8615)¶

Definition¶

A well-known URI is a URL with a path starting /.well-known/ reserved for site-wide metadata resources defined by IETF or industry-consensus standards. Codified by RFC 8615 (2019); registered at the IANA Well-Known URIs registry.

Authored by Mark Nottingham — notable because Mark Nottingham has been a Cloudflare principal engineer; Cloudflare's 2026-04-17 post explicitly credits him when surveying the /.well-known/ ecosystem of agent standards.

Purpose¶

For clients that need a metadata resource from an unknown origin, a fixed path convention avoids two broken alternatives:

Guess at likely URLs — /api.json, /openapi.yaml, /meta/... — unreliable, fragile across redesigns, adds lookup cost.
Scrape the home page — expensive, fragile, fails for non-HTML origins.

With well-known URIs, the client pins a single path per well-known resource and gets a predictable response without negotiation.

Core of the 2026 agent-ergonomic web¶

The 2026-04 Cloudflare post surfaces six well-known-URI-based standards that together define what "agent-ready" means at the discovery layer:

/.well-known/api-catalog — RFC 9727, list of public APIs + specs + docs.
/.well-known/mcp/server-card.json — draft MCP spec for pre-connect server description.
/.well-known/agent-skills/index.json — Cloudflare-authored RFC listing skill documents.
/.well-known/oauth-protected-resource — RFC 9728 OAuth-server discovery.
/.well-known/http-message-signatures-directory — Web Bot Auth friendly-bot public keys.
(Adjacent, but not under /.well-known/ for historical reasons) /robots.txt — crawl rules + sitemap pointer + Content Signals.

Cloudflare's canonical article quote:

"You might notice that the .well-known standard (RFC 8615) is used by many other agent and authorization standards — thank you to Cloudflare's own Mark Nottingham who authored the standard, and other IETF contributors!"

Umbrella pattern¶

Captured as patterns/well-known-endpoint-discovery — the umbrella pattern covering all six resources above, their Link:-header advertising, and the Agent Readiness Score's multi-dimension grading of their presence.

Seen in¶

sources/2026-04-17-cloudflare-introducing-the-agent-readiness-score-is-your-site-agent-ready — canonical wiki instance of the RFC 8615 convention as the substrate for an entire cluster of agent-ergonomic web standards. Six well-known endpoints scored / checked.

concepts/api-catalog / concepts/mcp-server-card / concepts/agent-skills-discovery / concepts/oauth-protected-resource-metadata — four of the six agent-era well-known URIs.
systems/web-bot-auth — the fifth (Web Bot Auth's signatures directory).
concepts/link-response-header — HTTP-layer advertising mechanism for well-known-URI resources.
concepts/agent-readiness-score — where the six are graded.
patterns/well-known-endpoint-discovery — umbrella pattern.