csoai/a2a-card-census

Current record: 0.1.1 — record.v0.1.1.json, sha256 4a2b46bb42aa727363ca04d8a2cc21ed76b50a4c6937a62f80d6fcfda191af91, supersedes record.json (0.1, sha256 b290b53d05912d8b3a5913c7e73e693f40cc71be8e0432c4626643c6d662176c), which stays published unchanged. Figures in sections 1–3 are 0.1 unless the Corrections section below restates them; the dataset viewer loads the 0.1.1 rows (data/cards.v0.1.1.jsonl.gz).

A2A agent card census - measured read, 2026-09-25

Every a2aregistry listing in our 2026-09-25 census frame (443 listings): whether its A2A agent card was served, and whether the card's signatures verify under a key the card itself points to, 2026-09-25T07:24:34Z to 2026-09-25T07:25:59Z, from one network location. Published by Council of AI (CSOAI). We measure. We do not certify, grade, rank or endorse any agent.

Read state: EXHAUSTED. All 443 listings reached exactly one state. The frame is one registry's listings; it is not a population total of A2A agents.

Record: record.json sha256 b290b53d05912d8b3a5913c7e73e693f40cc71be8e0432c4626643c6d662176c, signed (Ed25519, did:web:csoai.org#board-attestation-1) at 2026-09-25T08:22:33.567Z; OpenTimestamps state PENDING_CALENDAR_COMMITMENT at publication. The builder cross-checked the run summary against the row files (21 checks, all hold) before writing the record.

Siblings: csoai/mcp-remote-census (remote MCP endpoints listed in public catalogues), csoai/hf-mcp-spaces-census.

1. States (per listing)

state	listings	meaning
CARD_SERVED	422	a JSON object that parses as an agent card
ROBOTS_DISALLOWED	9	robots.txt forbids the card paths for CSOAI-census; only robots.txt was requested
NOT_FOUND	5	every candidate answered 404/410 (or another 4xx)
UNREACHABLE	5	DNS, refused, TLS, reset, 5xx, or an off-host redirect only
AUTH_REQUIRED	2	401/403 and no candidate served a card

States with zero listings: CARD_INVALID, HF_SPACE_NOT_CONTACTED, INVALID_URL, NON_PUBLIC_ADDRESS, TIMEOUT. Not contacted: no request to a host that resolves to a non-global address (checked for every candidate host) and none to *.hf.space (a request could wake a sleeping Space); robots.txt honoured. The one listing whose card URL is on *.hf.space is recorded UNREACHABLE, not HF_SPACE_NOT_CONTACTED, because its other candidate (an unqualified internal hostname from the listing's url) failed DNS. It received no request in this run; the DNS query for the internal name went to our resolver only.

2. Signatures (denominator: 422 cards served)

	cards	% of served
signed (at least one signature)	33	7.82
VERIFIED	18	4.27
FAILED	3
UNCHECKABLE	12
NO_SIGNATURES	389

Canonicalisation: JCS (RFC 8785) of the card with signatures removed; detached JWS (RFC 7515). VERIFIED by key source: jku 17, embedded_jwk 1 (embedded_jwk = the card vouches for its own key: integrity, not identity). FAILED = no verification over JCS(card without signatures) under the key the card points to; alt_serialisations_verifying is a diagnostic of 4 non-spec serialisations, never a pass. FAILED cards that verify under any of 4 non-spec serialisations: 0.

key source / result (per signature)	signatures
jku / VERIFIED	17
none / UNCHECKABLE	9
jku / FAILED	3
embedded_jwk / VERIFIED	1
did_web / UNCHECKABLE	1
jku / UNCHECKABLE	1
None / UNCHECKABLE	1

why UNCHECKABLE	signatures
no jku, no embedded jwk, no did:web kid: the card points to no key	9
key document has no key matching kid	2
signature object lacks protected/signature strings	1

Card protocolVersion is what the card declares (3 differ from their listing); no A2A call was made. No MCP request is made by this census. For the sibling MCP censuses: the current MCP specification revision is 2026-07-28 (checked 2026-09-25), and our MCP probers request 2025-11-25.

3. Anomalies, including a disclosed breach of our own rule

• B1 (DISCLOSED BREACH OF OUR OWN RULE (superseded run kept)) - Run 1 of this census (2026-09-25T07:18:59Z to 2026-09-25T07:19:54Z) applied the non-public-address check to the first candidate host only and did not exclude *.hf.space. It sent ONE request, GET /robots.txt, to vishalmysore-a2amcpdemo.hf.space without first reading the Space's stage from the Hub API - the stage check our rule requires. It also asked our resolver for the unqualified internal hostname in that listing; DNS failed and no connection was made. Run 1 is superseded by run 2 (this record) and kept for audit; its rows are not published as data.
• B2 - 2 served cards carry a signatures key with zero entries; they count as NO_SIGNATURES. So 35 cards have the key and 33 are signed.
• B3 - 7 listings the registry marks healthy served no card to us.
• B4 - 2 served cards are byte-identical to another listing's card (420 distinct of 422).
• B5 - 3 cards declare a protocolVersion different from their registry listing; declared values include strings that are not A2A release numbers (see cards_served.protocolVersion_declared).

Hub API read of that Space (the Hub API, not the Space itself): stage RUNTIME_ERROR at 2026-09-25T08:20:51Z. Run 1 is kept for audit (run/superseded-run1-summary.json, run/superseded-run1-SUPERSEDED.txt); its rows are not published as data.

4. What this is not evidence of

• that any agent works, is safe, is who it says, or does what its skills say
• that a VERIFIED signature proves identity: it proves only that the key the card points to signed these bytes (embedded_jwk: integrity only)
• that a FAILED or UNCHECKABLE card is malicious; it may be a canonicalisation or key-publication mistake
• endorsement, ranking, grading, or approval of any agent or operator
• a population total of A2A agents: the frame is one registry's listings on 2026-09-25
• reachability at any other moment or from any other network location

Files

file	rows	sha256
record.json		b290b53d05912d8b3a5913c7e73e693f40cc71be8e0432c4626643c6d662176c
data/cards.jsonl.gz	443	9d5eaf5bb0866aa16521f1b95064091ce9914d4f957ca75ef273063e4ee4f160
run/summary.json		f32890d749cde7c15dafd61ce848661b5a0aeac440b0289a32ff7796c3651c34
run/superseded-run1-summary.json		ac4a25a88a9a5b9280b26cbee90aa8b9642ce3d4a15caa80d63d6513bbec990d
run/superseded-run1-SUPERSEDED.txt		a773870ff1cdf49a5206da354a0cf3f742c42e40cff8c77e3aa35e42d48eb2f4

record.signed.json (signature), record.json.ots (OpenTimestamps proof), record.ots.json (its stated state). Rows in data/cards.jsonl.gz carry: order, id, host, state, reason, card_url, card_source, card_sha256, card_protocolVersion, listed_protocolVersion, signed, n_signatures, sig_state, verify_results, key_source_kinds, algs. They carry no card text (names, descriptions, skills); card_sha256 pins the card bytes we received. card_url is the URL the card was served from, or the listed wellKnownURI when none was served.

How to verify

Signature. In record.signed.json: serialise payload as JSON with keys sorted recursively, no whitespace, UTF-8. Its sha256 must equal signature.payload_sha256. payload.artifact.sha256 must equal sha256 of record.json, and payload.published_files pins every data file by sha256. Verify signature.sig_ed25519 (hex) over those bytes with the Ed25519 key #board-attestation-1 (publicKeyJwk.x, base64url) in https://csoai.org/.well-known/did.json. Change one byte of the payload and it must fail.

import json, hashlib, base64, urllib.request
from cryptography.hazmat.primitives.asymmetric import ed25519
s = json.load(open("record.signed.json"))
c = json.dumps(s["payload"], sort_keys=True, separators=(",", ":"), ensure_ascii=False).encode()
assert hashlib.sha256(c).hexdigest() == s["signature"]["payload_sha256"]
assert hashlib.sha256(open("record.json", "rb").read()).hexdigest() == s["payload"]["artifact"]["sha256"]
for f, h in s["payload"]["published_files"].items():
    assert hashlib.sha256(open(f, "rb").read()).hexdigest() == h, f
# csoai.org answers 403 to Python's default User-Agent, so send a named one
did = json.load(urllib.request.urlopen(urllib.request.Request("https://csoai.org/.well-known/did.json", headers={"User-Agent": "csoai-dataset-verify/1.0 (+https://huggingface.co/csoai)"})))
x = [m for m in did["verificationMethod"] if m["id"].endswith("#board-attestation-1")][0]["publicKeyJwk"]["x"]
pk = ed25519.Ed25519PublicKey.from_public_bytes(base64.urlsafe_b64decode(x + "=="))
pk.verify(bytes.fromhex(s["signature"]["sig_ed25519"]), c)   # must pass
from cryptography.exceptions import InvalidSignature
try:                                                          # control: one extra byte must fail
    pk.verify(bytes.fromhex(s["signature"]["sig_ed25519"]), c + b" ")
    raise SystemExit("CONTROL VERIFIED - do not trust this check")
except InvalidSignature:
    pass

Timestamp. pip install opentimestamps-client, then ots upgrade record.json.ots and ots verify record.json.ots (verification needs a Bitcoin node or a block explorer). At publication the proof held 3 pending calendar attestations from https://alice.btc.calendar.opentimestamps.org, https://bob.btc.calendar.opentimestamps.org, https://finney.calendar.eternitywall.com: a pending calendar commitment, not a Bitcoin attestation. It proves nothing about time until it is upgraded and verified against the chain.

Without a Bitcoin node (a full ots verify needs one), check an upgraded proof offline and compare the merkle root with a public block explorer (two independent ones is better):

# (a pending proof must first be upgraded: ots upgrade <proof>)
ots --no-bitcoin verify -f record.json record.json.bitcoin.ots
# -> "To verify manually, check that Bitcoin block H has merkleroot M"
B=$(curl -s -A "csoai-dataset-verify/1.0 (+https://huggingface.co/csoai)" https://mempool.space/api/block-height/H)
curl -s -A "csoai-dataset-verify/1.0 (+https://huggingface.co/csoai)" https://mempool.space/api/block/$B | python3 -c 'import sys,json;print(json.load(sys.stdin)["merkle_root"])'
# must print M; repeat against https://blockstream.info/api/...

Contact, objections and re-checks

• Contact: nicholas@csoai.org (Council of AI / CSOAI). Please name this dataset and the agent card URL or host you mean.
• Ask for a re-check. Reply with the agent card URL or host. We re-measure it with the same read-only instrument and run a tamper control beside it (a deliberately altered copy must fail the same check, or the re-check does not count). A dated re-check record is published only with your knowledge. Published rows are never edited in place: a correction is a new, signed file that supersedes the old one, and both stay visible.
• Object, or opt out of future probing. Name the agent card URL or host. It is added to the exclusion list (scripts/census/probe-exclusions.json in the census code, dated, public), and the next run honours it before sending any request and records the skip by name. The reader behind this dataset (scripts/census/a2a-card-probe.py) does not yet read that list in code; until it does, an entry is honoured by hand before the next run, and the skip is still recorded by name.
• Objections are recorded. Every objection, opt-out and re-check request is logged with its date and what was done; nothing is removed silently.

Citation

@misc{csoai_a2a_card_census_2026,
  author       = {{Council of AI (CSOAI)}},
  title        = {A2A agent card census: measured read of 2026-09-25},
  year         = {2026},
  publisher    = {Hugging Face},
  howpublished = {\url{https://huggingface.co/datasets/csoai/a2a-card-census}}
}

Licence

Data: CC-BY-4.0. Cite as: Council of AI (CSOAI), A2A agent card census, measured read 2026-09-25, csoai/a2a-card-census.

Timestamp status

Checked 2026-09-25T13:46Z by ots upgrade on a copy of each published pending proof. A pending .ots is never rewritten: an upgraded proof is published as a NEW file <name>.bitcoin.ots beside it. BITCOIN_ATTESTED means the proof carries a BitcoinBlockHeaderAttestation whose commitment (byte-reversed) equals the merkle root of the block header at that height as served by two independent public sources (blockstream.info and mempool.space; each raw header also double-SHA256s to the block hash it is served under). No local Bitcoin node was used. Details: ots-bitcoin-check-2026-09-25.json.

• record.json (sha256 b290b53d05912d8b3a5913c7e73e693f40cc71be8e0432c4626643c6d662176c): BITCOIN_ATTESTED at block 968527 (also blocks 968533, 968537, via other calendars) (checked against 2 header sources: blockstream.info, mempool.space). Upgraded proof: record.json.bitcoin.ots (sha256 fc4d44231bc385bf0b582484e868c211d936071f1b5caee3c111716068d141d3); the published pending proof record.json.ots is unchanged.
• Reconciliation: an earlier same-day upgrade of the same pending proofs is published under ots-upgraded/2026-09-25/ (checked against one header source). It commits to the same file digests; calendars can return different block paths, so the heights may differ. Either proof suffices; neither replaces the pending original.

Corrections

0.1.1 — 26 September 2026 (supersedes record.json 0.1; the 0.1 files stay published unchanged)

record.v0.1.1.json (sha256 4a2b46bb42aa727363ca04d8a2cc21ed76b50a4c6937a62f80d6fcfda191af91) supersedes record.json (sha256 b290b53d05912d8b3a5913c7e73e693f40cc71be8e0432c4626643c6d662176c). The rows are data/cards.v0.1.1.jsonl.gz; data/cards.jsonl.gz, record.json, record.signed.json, record.json.ots, record.ots.json and every other 0.1 file are kept byte for byte: superseded, not deleted, not edited.

Why. A2A spec 8.4.3 (Signature Verification) step 3 - 'Remove properties with default values from the received Agent Card' - was not applied by the 0.1 prober, which verified every card over JCS(card as served, minus signatures). Rule now: judge each card against the spec version it declares (ruling 2026-09-26). A card declaring 1.x (or nothing recognisable) is verified over the 8.4.3 payload (default values removed per the A2A proto, signatures excluded, JCS). A card declaring 0.x is verified over JCS of its served bytes: protocol 0.3 defines no canonicalisation step. Fix: scripts/census/a2a-card-probe.py commits 96959268d, 33d0dfa64.

Check. The 0.1 row projection over the stored run reproduces the published 0.1 rows byte for byte. 19 signed cards (those whose payload step 3 alters) were re-checked on their stored bytes; key documents were re-fetched 2026-09-26 and the 0.1 rule on them reproduces every 0.1 verdict, so no change below is a key rotation. Every other card has the same signing input under both rules.

Agents whose verdict changes: 7 (VERIFIED -> FAILED: 6, FAILED -> VERIFIED: 1)

agent id (a2aregistry)	host	declares	0.1	0.1.1	why
fbbc1e43-6975-46d2-a066-7e8ad90357b3	api.getemboss.ai	1.x	VERIFIED	FAILED	declares 1.x: A2A 8.4.3 step 3 (remove default values) applied; the signature was made over the served bytes WITH default values, so it no longer verifies
ee821d2a-b667-40b7-9dda-b1170aaefa7f	philongevity.com	1.x	FAILED	VERIFIED	declares 1.x: A2A 8.4.3 step 3 (remove default values) applied; the signature was made over the card with default values removed, as 8.4.1-8.4.2 require, and now verifies
6f97c159-43ed-49de-92b6-1d5aa5ae8ce7	www.smklog.com	1.x	VERIFIED	FAILED	declares 1.x: A2A 8.4.3 step 3 (remove default values) applied; the signature was made over the served bytes WITH default values, so it no longer verifies
41d157e0-cdec-4431-a6e1-07e070f35b08	api.cogdepot.com	1.x	VERIFIED	FAILED	declares 1.x: A2A 8.4.3 step 3 (remove default values) applied; the signature was made over the served bytes WITH default values, so it no longer verifies
125be81b-7326-41cd-85a2-7e0c2aa031b8	agent.co-legal.be	1.x	VERIFIED	FAILED	declares 1.x: A2A 8.4.3 step 3 (remove default values) applied; the signature was made over the served bytes WITH default values, so it no longer verifies
77c18a1a-bc34-4314-9cd3-8192f9f288a2	emem.dev	1.x	VERIFIED	FAILED	declares 1.x: A2A 8.4.3 step 3 (remove default values) applied; the signature was made over the served bytes WITH default values, so it no longer verifies
ee3508f9-9a8d-4221-8668-fef137ff9fff	planets.agentexchange.work	1.x	VERIFIED	FAILED	declares 1.x: A2A 8.4.3 step 3 (remove default values) applied; the signature was made over the served bytes WITH default values, so it no longer verifies

Cards declaring 0.3 that keep their verdict, with a note:

agent id	host	verdict (declared 0.3)	under 1.x rules	note
87426082-ec97-488d-beea-1bd717216445	codex-autonomous-worker.rwdburley.chatgpt.site	VERIFIED	FAILED	protocol 0.3 defines no canonicalisation step; verdict under the declared version; under 1.x rules this card would FAIL
c59ee47c-4565-4fa9-bf98-807b0501c58a	b612-a2a.vercel.app	VERIFIED	FAILED	protocol 0.3 defines no canonicalisation step; verdict under the declared version; under 1.x rules this card would FAIL
f9da91fd-c17c-4dd2-8349-f5fd53108d5c	api1.ilovechicken.co.uk	VERIFIED	FAILED	protocol 0.3 defines no canonicalisation step; verdict under the declared version; under 1.x rules this card would FAIL

Signature counts, 0.1 → 0.1.1 (denominator: 422 cards served):

	0.1	0.1.1
verified	18	13
failed	3	8
uncheckable	12	12
no_signatures	389	389
signed	33	33
pct_verified	4.27	3.08

Verify. record.v0.1.1.signed.json: Ed25519 under did:web:csoai.org#board-attestation-1 (signed_at 2026-09-26T04:06:22.149Z); its payload carries supersedes_sha256. record.v0.1.1.json.ots: 3 pending calendar attestations at publication — a pending calendar commitment, not a Bitcoin attestation. Per-card evidence: correction.v0.1.1.evidence.json.