Correction: the MCP registry read in this dataset was 2 pages, not complete

totals.json said mcp_registry_enumeration_complete: true from 2 pages / 100 entries. A full read on 2026-09-25 walked 359 pages (35,873 latest-version servers). Producer fixed on lane census-frame-20260925. Original bytes at cc1dcf041b9a1f61807e434759bd700be3007b2d.

CORRECTION.md

@@ -0,0 +1,82 @@
+# Correction: `csoai/agent-interop-census` claims a complete MCP registry read from 2 pages
+
+**Status: CORRECTED 2026-09-25.** This dataset now carries this note, a README banner, and `totals.json` with `mcp_registry_enumeration_complete: false`. The original bytes remain at revision `cc1dcf041b9a1f61807e434759bd700be3007b2d`.
+Until it is republished, do not quote any `mcp_registry_*` figure from it as a total.
+
+## The published claim
+
+`totals.json` in the Hugging Face dataset `csoai/agent-interop-census`, revision
+`cc1dcf041b9a1f61807e434759bd700be3007b2d` (lastModified 2026-09-14T10:48:18Z, `as_of`
+2026-09-14T10:48:11Z), read on 2026-09-25:
+
+| field | published value |
+|---|---|
+| `mcp_registry_unique_entries` | `100` |
+| `mcp_registry_pages_read` | `2` |
+| `mcp_registry_stop_reason` | `"cursor exhausted — clean end of registry"` |
+| `mcp_registry_enumeration_complete` | **`true`** |
+| `rows_by_source.modelcontextprotocol-registry` | `100` |
+
+The dataset card built from it also says "This build's registry enumeration is COMPLETE".
+
+## What was measured
+
+| read | when (UTC) | pages | rows | read_state |
+|---|---|---|---|---|
+| survey walk, `version=latest` | 2026-09-25 05:24 to 05:31 | 359 | 35,870 | cursor exhausted |
+| `scripts/census/frame.py`, `version=latest` | 2026-09-25, run of `/evac-bulk/census-frame-2026-09-25/` | 359 | **35,873** | **EXHAUSTED** (every page HTTP 200 with `servers[]` and `metadata{}`; `nextCursor` absent on page 359) |
+
+The frame run's page set digest is `60482de9b0b1121b6532d24721d2f2911393816466427bb734d11c5333d52ffb`
+(sha256 of the 359 page sha256s, one per line, in order). The raw pages are kept on
+oracle-micro-2 under `/evac-bulk/census-frame-2026-09-25/raw/mcp-registry/`.
+
+**The units differ, so this note does not state a ratio.** The published figure counts
+`(name, version)` pairs across all versions. The measured figure counts latest-version servers.
+The all-versions population was **not** re-measured here. Every latest server is one
+`(name, version)` pair, so that population is at least 35,873. That is a floor, not a total.
+What the measurement does settle is that a 2-page, 100-entry read was not a complete read of
+the registry.
+
+## The producer, and the fix
+
+The published case comes from the collector, `scripts/census/collect-mcp-registry.py`:
+it parsed any JSON body as a page, never checked the HTTP status or the page shape, and
+recorded "no `metadata.nextCursor`" as `cursor exhausted — clean end of registry`. Page 2 added
+no new rows and carried no `nextCursor`. The collector kept no response bodies, so whether page 2
+was an error object or an empty page cannot be recovered. Either way it was not the end.
+
+The builder, `scripts/census/build-agent-interop-census.py`, then set
+`mcp_registry_enumeration_complete = stop_reason != "in-progress"`. Under that test every
+non-checkpoint stop counts as complete: a fetch failure, a repeated cursor, or the bounded
+fallback file `/tmp/mcp_census2.json`.
+
+Fixed on lane `census-frame-20260925`. Both fixes fail closed:
+
+- `collect-mcp-registry.py`: a response counts as a page only if it is HTTP 200, complete
+  JSON, and has `servers[]` and `metadata{}`. Anything else stops the walk as PARTIAL. The
+  collector now writes `read_state` and `pages_valid` explicitly.
+- `read_state.py` (new): `walk_read_state()` returns EXHAUSTED only if the collector wrote
+  `read_state: EXHAUSTED` and `pages_valid == pages`. Legacy files without `read_state`,
+  including the one behind the published figures, are PARTIAL. So is the bounded fallback file.
+- `build-agent-interop-census.py` now publishes `mcp_registry_read_state` and derives
+  `mcp_registry_enumeration_complete` from it. `mcp_registry_population_total` is null
+  unless the read is EXHAUSTED. The same applies to `hf_spaces_read_state`.
+- `collect-hf-spaces.py` had the same failure mode: a non-JSON body or an error object ended
+  the loop silently, and a 400-page cap was never reported. It now writes `read_state` too.
+- Tests: `scripts/census/test_frame.py` → `CensusReadState` (the published legacy document
+  evaluates to PARTIAL), plus `RegistryWalk.test_error_object_is_not_an_end`.
+
+## Other published figures this does not re-measure
+
+- `huggingface-spaces: 6,588` came from `search=mcp`. That query differs from the frame's
+  `filter=mcp-server` (10,822, EXHAUSTED), so the two numbers are not comparable. The old HF
+  collector recorded no read state, so treat 6,588 as a read count, not a population.
+- `smithery_unique_collected: 272` against `smithery_declared_total: 14,625` was already
+  labelled as capped. The frame reads the same cap (500 rows served, 264 distinct, declared
+  17,186) and records it as PARTIAL.
+
+## To close this note
+
+Rebuild with the fixed collector and builder, confirm that `mcp_registry_read_state` is
+`EXHAUSTED`, and republish with this note linked from the card. Every row stays an index
+entry: DISCOVERED and UNMEASURED.

README.md

@@ -23,6 +23,8 @@ configs:
     path: census.jsonl
 ---
 
+> **CORRECTION (2026-09-25).** The MCP registry figures in this dataset are **not** a complete read. `totals.json` said `mcp_registry_enumeration_complete: true` from 2 pages and 100 entries; a full read on 2026-09-25 walked 359 pages and found **35,873 latest-version servers** (a different unit — the published 100 counted name+version pairs — so no ratio is stated). The collector treated an error or empty page as the end of the registry; that producer is fixed. Do not quote any `mcp_registry_*` figure below as a total. Details: [`CORRECTION.md`](CORRECTION.md); measured read: [`census-frame-2026-09-25/summary.json`](census-frame-2026-09-25/summary.json). Original bytes: revision `cc1dcf041b9a1f61807e434759bd700be3007b2d`.
+
 <!-- csoai-hubcard-v2 -->
 
 # Agent Interop Census

census-frame-2026-09-25/summary.json

@@ -0,0 +1,154 @@
+{
+  "schema": "csoai.census-frame/0.1",
+  "run_started": "2026-09-25T05:45:50Z",
+  "run_finished": "2026-09-25T05:54:05Z",
+  "user_agent": "CSOAI-census/0.1 (+https://councilof.ai)",
+  "min_interval_s": 1.0,
+  "requests": 384,
+  "retry_after_waits": 0,
+  "sources": {
+    "mcp-registry": {
+      "read_state": "EXHAUSTED",
+      "reason": "metadata.nextCursor absent on page 359: upstream end",
+      "declared_total": null,
+      "rows_read": 35873,
+      "distinct_ids": 35873,
+      "duplicates_skipped": 0,
+      "population_total": 35873,
+      "pages": 359,
+      "pages_valid": 359,
+      "page_set_sha256": "60482de9b0b1121b6532d24721d2f2911393816466427bb734d11c5333d52ffb",
+      "seconds": 464.0,
+      "distinct_endpoints": 21958,
+      "endpoint_listings": 22353,
+      "entries_without_endpoint": 14063,
+      "endpoint_rejects": {
+        "templated host": 122
+      }
+    },
+    "hf-spaces": {
+      "read_state": "EXHAUSTED",
+      "reason": "no rel=next Link after page 11: upstream end",
+      "declared_total": null,
+      "rows_read": 10822,
+      "distinct_ids": 10822,
+      "duplicates_skipped": 0,
+      "population_total": 10822,
+      "pages": 11,
+      "pages_valid": 11,
+      "page_set_sha256": "a6297b951e5c7660c9663d1159b39f80181597dbca1a583f44d6423811aea2fc",
+      "seconds": 10.7,
+      "distinct_endpoints": 10822,
+      "endpoint_listings": 10822,
+      "entries_without_endpoint": 0,
+      "endpoint_rejects": {}
+    },
+    "a2aregistry": {
+      "read_state": "EXHAUSTED",
+      "reason": "offset reached declared total 443; 443 distinct ids == declared",
+      "declared_total": 443,
+      "rows_read": 443,
+      "distinct_ids": 443,
+      "duplicates_skipped": 0,
+      "population_total": 443,
+      "pages": 5,
+      "pages_valid": 5,
+      "page_set_sha256": "9363da3cb7ebd07c9de57333d449eae9366824beec89becc59230cab0014e9f9",
+      "seconds": 5.3,
+      "distinct_endpoints": 440,
+      "endpoint_listings": 443,
+      "entries_without_endpoint": 0,
+      "endpoint_rejects": {}
+    },
+    "docker-mcp-registry": {
+      "read_state": "EXHAUSTED",
+      "reason": "commit 49b643ce3fc7: tree lists 328 servers/*/server.yaml; tarball of the same commit parsed all 328",
+      "declared_total": 328,
+      "commit": "49b643ce3fc73e6ee80bb962719b6e2990e3d397",
+      "rows_read": 328,
+      "distinct_ids": 328,
+      "duplicates_skipped": 0,
+      "population_total": 328,
+      "pages": 3,
+      "pages_valid": 1,
+      "page_set_sha256": "84d9a779dbba9a6763428696dbfcaa52de380229f48633bc02ea245f05447654",
+      "seconds": 6.1,
+      "distinct_endpoints": 77,
+      "endpoint_listings": 77,
+      "entries_without_endpoint": 251,
+      "endpoint_rejects": {}
+    },
+    "smithery": {
+      "read_state": "PARTIAL",
+      "reason": "anonymous API advertises totalPages=5 at pageSize 100 (500 rows served, 264 distinct) against declared totalCount=17186; page 6 returned 0 servers. The listing carries no endpoint URL. Reading further needs an API key.",
+      "declared_total": 17186,
+      "rows_read": 500,
+      "distinct_ids": 264,
+      "duplicates_skipped": 236,
+      "population_total": null,
+      "pages": 6,
+      "pages_valid": 5,
+      "page_set_sha256": "f78a5f7f1658417279b96a72bd1b6604b7414b92f0a0318f2dc651a7ffe1e789",
+      "seconds": 5.4,
+      "distinct_endpoints": 0,
+      "endpoint_listings": 0,
+      "entries_without_endpoint": 264,
+      "endpoint_rejects": {}
+    }
+  },
+  "union": {
+    "endpoints_in_file": 33261,
+    "hosts_in_file": 25526,
+    "population_total": null,
+    "population_total_null_because": [
+      "smithery: PARTIAL"
+    ],
+    "note": "endpoints_in_file counts rows of endpoints.jsonl.gz - what was read. It is a population total only when population_total is non-null."
+  },
+  "overlap": {
+    "endpoint_level": {
+      "n": 33261,
+      "listed_by_k_catalogues": {
+        "1": 33225,
+        "2": 36
+      },
+      "in_2plus_catalogues": 36,
+      "pairwise": {
+        "a2aregistry&mcp-registry": 4,
+        "docker-mcp-registry&mcp-registry": 32
+      },
+      "combinations_2plus": {
+        "docker-mcp-registry+mcp-registry": 32,
+        "a2aregistry+mcp-registry": 4
+      }
+    },
+    "host_level": {
+      "n": 25526,
+      "listed_by_k_catalogues": {
+        "1": 25264,
+        "2": 262
+      },
+      "in_2plus_catalogues": 262,
+      "pairwise": {
+        "a2aregistry&mcp-registry": 223,
+        "docker-mcp-registry&mcp-registry": 36,
+        "hf-spaces&mcp-registry": 3
+      },
+      "combinations_2plus": {
+        "a2aregistry+mcp-registry": 223,
+        "docker-mcp-registry+mcp-registry": 36,
+        "hf-spaces+mcp-registry": 3
+      }
+    }
+  },
+  "canonicalisation": "scheme + lowercased host (+non-default port) + path; query and fragment dropped; '{var}' -> '{}' (flagged templated); trailing '/' removed; templated host = reject. HF Spaces rows carry the Space base URL https://<subdomain>.hf.space/, not a declared MCP path, so they meet registry rows at host level, rarely at endpoint level.",
+  "not_read_by_this_frame": {
+    "x402 bazaars": "read to exhaustion daily by scripts/census/x402-bazaar-conformance.py"
+  },
+  "what_a_row_is": "an endpoint URL a public catalogue lists. DISCOVERED, UNMEASURED.",
+  "what_it_never_proves": "that the endpoint is live, speaks its protocol, is safe, or is good.",
+  "files": {
+    "entries.jsonl.gz": "7932d3c69a283b9d04e581d37acd4d50526a32b9a7a1048ba6fe788c032c7e15",
+    "endpoints.jsonl.gz": "d8d230f4b3f2a02d90230928e78284e6c20af0677a7b7561f79f134d95e1b9b3"
+  }
+}

totals.json

@@ -13,7 +13,7 @@
   "mcp_registry_pages_read": 2,
   "mcp_registry_source_file": "/tmp/mcp_census_full.json",
   "mcp_registry_stop_reason": "cursor exhausted \u2014 clean end of registry",
-  "mcp_registry_enumeration_complete": true,
+  "mcp_registry_enumeration_complete": false,
   "mcp_registry_is_latest": 65,
   "mcp_registry_exposing_remote_endpoint": 342,
   "hf_spaces_pages_read": 66,
@@ -48,5 +48,22 @@
   "glama_excluded": "401 without an API key, and its API Data Licence requires visible Glama attribution on every page displaying the data. Not collected.",
   "reachability_observation": null,
   "graded_rows": 0,
-  "grading_note": "Zero rows carry a measurement. This is a census: an index of what exists and is publicly reachable. A grade requires a run against a frozen bank, and none was done here."
-}
+  "grading_note": "Zero rows carry a measurement. This is a census: an index of what exists and is publicly reachable. A grade requires a run against a frozen bank, and none was done here.",
+  "correction": {
+    "date": "2026-09-25",
+    "file": "CORRECTION.md",
+    "prior_revision": "cc1dcf041b9a1f61807e434759bd700be3007b2d",
+    "was": {
+      "mcp_registry_enumeration_complete": true,
+      "mcp_registry_pages_read": 2,
+      "mcp_registry_unique_entries": 100
+    },
+    "measured_2026_09_25": {
+      "source": "census-frame-2026-09-25/summary.json",
+      "pages": 359,
+      "latest_version_servers": 35873,
+      "read_state": "EXHAUSTED",
+      "note": "different unit from the published 100 (name+version pairs); 35,873 is a floor for that population"
+    }
+  }
+}