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Signature Agent Card (Web Bot Auth registry)

Identify This draft defines the "Signature Agent Card": a JSON metadata document that a Web Bot Auth signer (a crawler, agent, or bot operator) publishes to describe itself — its identity, purpose, expected request rate, and cryptographic keys [1]. Rather than inventing a new schema, it reuses the OAuth Dynamic Client Registration Metadata field set (client_id, client_name, client_uri, logo_uri, contacts, jwks_uri/jwks) and extends it with a single web_bot_auth object (fields observed in the spec include expected-user-agent, an RFC 9309 robots.txt product token, a trigger type such as "fetcher", and a purpose such as "tdm" for text-and-data-mining) [1]. The same document also formally establishes an IANA registry for that web_bot_auth object's members, so third parties can register new fields.

Overview

It solves the metadata gap left by the base Web Bot Auth signature protocol: RFC 9421 signatures and the Signature-Agent header prove that a request was signed by a given key, but not who holds that key, why they are crawling, or how fast they intend to request — this card supplies that context in a machine-readable form at the same well-known path used for the key directory [1]. It does not itself carry the cryptographic proof (that is RFC 9421 plus the base Web Bot Auth protocol) and does not define enforcement — a site is free to ignore the declared purpose or rate.

Current state: an individual Internet-Draft, draft-meunier-webbotauth-registry-03, published 2026-06-26, authored by engineers at Cloudflare and Amazon [1]. As of this check (2026-09-06) it has not been adopted by the newly chartered IETF webbotauth Working Group, unlike its sibling protocol draft, which was adopted as a WG document on 2026-09-01 [2]. Its examples show the same well-known path (/.well-known/http-message-signatures-directory) can list multiple signer cards — individual bots as well as "platform" gateways that sign on behalf of several downstream operators.

Implementers: as an Informational registry-and-schema draft rather than a running protocol, no dedicated client/server implementations beyond the base Web Bot Auth signing/verifying stack (Cloudflare's libraries, see the sibling httpsig-protocol record) were found in this pass; none is claimed in the draft itself.

Disputed or unknown: whether this draft will be folded into the WG's adopted protocol document or remain a separate track, and how much of the web_bot_auth extension object will change before any WG adoption, are both open.

Discovery and probe

jwks_uri client-metadata field (or a plain client_id JSON document) resolvable at a well-known path · /.well-known/http-message-signatures-directory

GET https://{origin}/.well-known/http-message-signatures-directory
parse:     JSON object with OAuth Dynamic Client Registration fields (client_id, client_name, client_uri, jwks_uri or jwks, contacts) plus a web_bot_auth extension object (e.g. expected-user-agent, rfc9309-product, trigger, purpose)
on absent: No Signature Agent Card is published; a verifier can still validate the raw signature via the plain key directory but has no machine-readable identity, purpose or rate-limit metadata for the signer

Live check run by the MCP probe: GET /.well-known/http-message-signatures-directory. The Signature Agent Card adds OAuth client registration fields to the directory.

{
 "path": "/.well-known/http-message-signatures-directory",
 "expect": {
  "json_keys": [
   "client_name"
  ]
 },
 "note": "The Signature Agent Card adds OAuth client registration fields to the directory."
}

History

Instances

Every instance with its source is listed on the instances page.

See also

References

  1. The draft defines the Signature Agent Card as a JSON metadata document reusing OAuth Dynamic Client Registration Metadata fields extended with a single web_bot_auth object, and registers that object with IANA — https://www.ietf.org/archive/id/draft-meunier-webbotauth-registry-03.html (2026-06-26) VERIFIED
  2. As of this check the document remains an individual submission (not yet a webbotauth WG document), unlike the sibling httpsig-protocol draft which was WG-adopted on 2026-09-01 — https://datatracker.ietf.org/doc/draft-meunier-webbotauth-registry/ (2026-09-06) VERIFIED

Disputed: The seed record's name implied this was the identity card format only; the draft text shows it also functions as the IANA registry establishment document for the web_bot_auth metadata namespace, and its examples show operators listing multiple bot/platform cards (crawlers, gateways) at a shared discovery path, not just one card per origin.

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