Well-known URI
A well-known URI is a path beginning /.well-known/ at the root of an origin, reserved by RFC 8615 (May 2019, obsoleting RFC 5785) so that applications needing site-wide metadata do not have to negotiate arbitrary paths or risk colliding with a site's existing URL space. In the agentic web (Step 1, Discover), also known as .well-known, /.well-known/, it is implemented or referenced by Agent2Agent Protocol (A2A), Agentic Resource Discovery (ARD), AI Catalog well-known file.
Discover A well-known URI is a path beginning /.well-known/ at the root of an origin, reserved by RFC 8615 (May 2019, obsoleting RFC 5785) so that applications needing site-wide metadata do not have to negotiate arbitrary paths or risk colliding with a site's existing URL space. Anyone minting a new well-known name is expected to register it with IANA, referencing the specification that defines its format and media type; the mechanism itself defines no content at /.well-known/ and clients should not assume anything exists there by default. The agentic web reuses this pattern heavily: /.well-known/agent-card.json (A2A), /.well-known/ard.json and its predecessor /.well-known/ai-catalog.json (ARD), and others each register or informally claim a name under this prefix rather than inventing a new discovery convention. Used by: a2a, ard, ai-catalog-well-known-file.
Overview
A well-known URI is a path beginning /.well-known/ at the root of an origin, reserved by RFC 8615 (May 2019, obsoleting RFC 5785) so that applications needing site-wide metadata do not have to negotiate arbitrary paths or risk colliding with a site's existing URL space. In the agentic web (Step 1, Discover), also known as .well-known, /.well-known/, it is implemented or referenced by Agent2Agent Protocol (A2A), Agentic Resource Discovery (ARD), AI Catalog well-known file.
Instances
- Agent Community / Open Agent Registry (AID) · Observed 2026-10-23 · registry / facilitator
- Mnemom Cryptographic Agent Trust Service · Observed 2026-10-23 · trust authority
- Neuronto Agentic Web Index · Observed 2026-10-23 · registry / facilitator
- Salespeak B2B Buyer Concierge Agent · Observed 2026-10-23 · autonomous agent
- IBM BeeAI Multi-Agent Runtime · Observed 2026-08-29 · autonomous agent
- CopilotKit · Observed 2026-08-14 · client / harness
- 8004.org / ERC-8004 Trustless Agents Registry · Observed 2026-08-13 · registry / facilitator
- Google Agent Development Kit (ADK) · Observed 2026-07-31 · client / harness
- AGNTCY Agent Directory Service (Linux Foundation) · Observed 2026-07-23 · registry / facilitator
- Nevermined x402 Facilitator and Metering Clearinghouse · Observed 2026-07-23 · registry / facilitator
- GoDaddy Agent Name Service (ANS) Authority · Observed 2026-07-15 · trust authority
- Infoblox DNS-AID Registry (Linux Foundation) · Observed 2026-07-15 · registry / facilitator
See also
References
- https://www.rfc-editor.org/rfc/rfc8615 (2019-05) VERIFIED
Frequently asked questions
- What is Well-known URI?
- A well-known URI is a path beginning /.well-known/ at the root of an origin, reserved by RFC 8615 (May 2019, obsoleting RFC 5785) so that applications needing site-wide metadata do not have to negotiate arbitrary paths or risk colliding with a site's existing URL space. In the agentic web (Step 1, Discover), also known as .well-known, /.well-known/, it is implemented or referenced by Agent2Agent Protocol (A2A), Agentic Resource Discovery (ARD), AI Catalog well-known file.
- Which agentic web standards use Well-known URI?
- Well-known URI is used or referenced by Agent2Agent Protocol (A2A), Agentic Resource Discovery (ARD), AI Catalog well-known file. See https://agenticweb.wiki/terms/well-known/ for sourced definitions and verified implementations.
- How is Well-known URI verified on agenticweb.wiki?
- The Well-known URI record cites 1 primary specification or implementation source and was last verified on 2026-10-30.