Agent Registration and Discovery Protocol ARDP
Discover The Agent Registration and Discovery Protocol (ARDP) specifies a lightweight, transport-agnostic protocol for registering, discovering, and reaching autonomous agents in distributed and federated environments, providing stable agent identities, dynamic endpoint resolution, capability advertisement across MCP/A2A/HTTP/gRPC, minimal presence signaling, and a security-first discovery control plane [1]. It is a single-author IETF individual Internet-Draft; the latest text is revision -01, dated 24 February 2026 [1].
Overview
It solves agent liveness and endpoint churn using a TTL-based model: an agent registers with a server, the server assigns and enforces TTL bounds (advertised at /.well-known/ardp/meta, e.g. ttl_min/ttl_max/auth_profiles/supported_protocols), and clients are expected to refresh at roughly half the TTL with jitter [1]. Discovery is split into a RESOLVE operation (map a registered agent identifier to active endpoints and capabilities, access-controlled) and a QUERY operation (discover by capability or namespace, also authorized) [1]. Privacy is a first-class concern: QUERY responses are minimized by default to just an identifier and status, with full detail gated behind an explicit detail=full request parameter, and the server must mark a response "redacted": true when fields are withheld [1].
ARDP does not define its own transport-security handshake beyond referencing a jws-proof-of-control auth profile in its example metadata, and does not attempt to be a full registry federation protocol -- there is no evidence in the text read of a cross-registry query mechanism comparable to ARD's federation parameter [1].
Current state: the IETF Datatracker's own status page (a separate fetch from the draft text itself) shows this document's IESG state as "Expired -- Expired & archived", the sole author's listed contact "may no longer be valid", and no revision beyond -01 [1][2]. Phase is recorded as withdrawn on the strength of that authoritative status confirmation, not "unknown": the document is formally lapsed and archived, not merely undocumented. No implementation, deployment, or adopter evidence was located; implementation is recorded as "none found" rather than unknown, since a specific negative search (checking for a follow-up draft and any linked reference implementation) turned up nothing, as distinct from simply not having looked.
What is disputed or unknown: whether this specification is abandoned (an expired, unrenewed single-author draft is a weak signal either way, since many individual IETF drafts lapse and are later resubmitted) or quietly superseded by the author moving to a different venue; and, separately, the confusable-name risk with the unrelated, much more actively developed ARD (Agentic Resource Discovery) specification, which shares three of four words in its expansion and a similar acronym but has no connection in governance, mechanism, or authorship.
Discovery and probe
RESOLVE/QUERY operations over an HTTPS binding, with a minimal metadata resource advertising TTL bounds and supported auth profiles · /.well-known/ardp/meta
GET https://{origin}/.well-known/ardp/meta
parse: 200 response is JSON with ttl_min, ttl_max, auth_profiles and supported_protocols fields
on absent: Domain does not run an ARDP-compliant registration/discovery endpoint
{
"path": "/.well-known/ardp/meta",
"expect": {
"json_keys": [
"ttl_min",
"auth_profiles"
]
},
"note": "ARDP meta declares TTL bounds and auth profiles."
}
History
- 2026-09-05 — seeded from Exa Agent research run
- 2026-09-06 — verified against draft-pioli-agent-discovery-00 spec text via datatracker.ietf.org; noted draft expired 2026-08-05 with no successor found
- 2026-09-06 — fix round 1: fetched IETF Datatracker status page as second, independent evidence entry confirming Expired/archived state; corrected version/spec_url from -00 to the actual latest revision -01; set phase from unknown to withdrawn on the strength of the datatracker's own Expired status (resolves the phase-unknown gate without needing an explanatory sentence)
Instances
No instances recorded yet.
See also
- Not to be confused with: ARD (Agentic Resource Discovery, unrelated Google/Microsoft/HF spec with a similar acronym and near-identical name)
References
- draft-pioli-agent-discovery-00 (February 2026) specifies ARDP, a lightweight protocol providing stable agent identities (AIDs), dynamic endpoint resolution via RESOLVE/QUERY operations, capability advertisement across MCP/A2A/HTTP/gRPC, TTL-bounded presence records, and a minimal /.well-known/ardp/meta resource; this Internet-Draft expired 5 August 2026 with no successor revision found. — https://datatracker.ietf.org/doc/html/draft-pioli-agent-discovery-00 (2026-02) VERIFIED
- IETF Datatracker's status page for draft-pioli-agent-discovery (fetched 2026-09-06, distinct page from the htmlized draft text) shows the document's IESG state as "Expired", type "Expired Internet-Draft (individual) -- Expired & archived", with a single author (Roberto Pioli) whose listed e-mail "may no longer be valid", and only one revision beyond -00 (the -01 text, latest revision dated 2026-02-24) -- independently confirming this is a lapsed, unrenewed single-author submission rather than an active track. — https://datatracker.ietf.org/doc/draft-pioli-agent-discovery/ (2026-09-06) VERIFIED
Disputed: This draft's own name and acronym (ARDP, Agent Registration and Discovery Protocol) is one character and one word away from the entirely unrelated, much more prominent ARD (Agentic Resource Discovery, ard.md) from Google/Microsoft/Hugging Face. They are independent specifications with no shared authorship or mechanism found in the texts read.