{ "name": "MCP registry list walk - per-page receipt chain", "version": "1.0", "path": "/v1/registry-walk", "servedBy": "https://penny-surface-contract.penny-mcamp.workers.dev/v1/registry-walk", "measured_at": "2026-10-21T23:52:04Z", "endpoint": "https://registry.modelcontextprotocol.io/v0/servers", "method": { "what": "One anonymous client walked the registry's server list endpoint to cursor exhaustion, one page every >=1 second, page size 100, no credentials, no third-party MCP server contacted. Each page's body was saved; each page's cursor was recorded both in and out.", "page_size": 100, "credentials_sent": false, "third_party_servers_contacted": 0, "termination": "cursor_exhausted", "pages_logged": 480, "transient_failures": 2, "transient_failure_rule": "A non-2xx page or a transport timeout is NOT an end-of-cursor. Each failure was retried AT THE SAME cursor and recorded with its status, its file and its elapsed time; the chain contains no gap where a failure sits." }, "counts": { "pages": 480, "rows_served": 47944, "unique_name_at_version": 47944, "duplicate_name_at_version": 0, "rows_with_at_least_one_remote": 31334, "rows_with_at_least_one_package": 18372, "rows_with_neither": 512, "remote_entries": 32105, "remote_types": { "streamable-http": 30999, "sse": 1106 }, "distinct_remote_hosts": 22950, "arithmetic_check": "479 full pages x 100 + last page 44 = 47944" }, "concentration": { "note": "Remote rows are heavily concentrated in a few hosts, so a count of remote rows is NOT a count of independent operators. This is printed so the bigger number is not read as a bigger market.", "top_hosts_by_remote_entries": [ { "host": "agent-observatory-sensor.nolimit-observatory.workers.dev", "remote_rows": 2365, "share_of_remote_rows": 0.0755 }, { "host": "gateway.pipeworx.io", "remote_rows": 1878, "share_of_remote_rows": 0.0599 }, { "host": "api.mcp.ai", "remote_rows": 1116, "share_of_remote_rows": 0.0356 }, { "host": "mcp.apify.com", "remote_rows": 434, "share_of_remote_rows": 0.0139 }, { "host": "api.m2mcent.com", "remote_rows": 276, "share_of_remote_rows": 0.0088 }, { "host": "server.smithery.ai", "remote_rows": 217, "share_of_remote_rows": 0.0069 }, { "host": "a2awire.com", "remote_rows": 120, "share_of_remote_rows": 0.0038 }, { "host": "modevc.com", "remote_rows": 88, "share_of_remote_rows": 0.0028 }, { "host": "mcp.zovo.one", "remote_rows": 79, "share_of_remote_rows": 0.0025 }, { "host": "tooloracle.io", "remote_rows": 57, "share_of_remote_rows": 0.0018 } ], "top3_share_of_remote_entries": 0.171 }, "transient_failures": [ { "page": 145, "kind": "failure", "status": 500, "error": "HTTPError", "body_prefix": "{\"title\":\"Internal Server Error\",\"status\":500,\"detail\":\"Failed to get registry list\"}\n", "cursor_in": "guru.goanywhere/storefront:0.1.0", "elapsed_seconds": 11.64, "at": "2026-10-21T23:44:24Z", "recovery": "retried at this same cursor; the page that follows in chain[] carries cursor_in equal to this row's cursor_in and is the recovered read" }, { "page": 479, "kind": "failure", "status": null, "error": "URLError: ", "body_prefix": null, "cursor_in": "xyz.apexfaucet/apex-evm:1.0.6", "elapsed_seconds": 59.907, "at": "2026-10-21T23:51:53Z", "recovery": "retried at this same cursor; the page that follows in chain[] carries cursor_in equal to this row's cursor_in and is the recovered read" } ], "receipt": { "chain_root_sha256": "cb40a9184e4d21a1d180673a30f9e4b6649664c1c259e5ca0efa3d6153606911", "names_root_sha256": "6105080a239fdb451274dc5bc5fbd94e28c6e91c060d3b2914cead4adf4669b9", "what_the_roots_cover": "chain_root is sha256 over the 480 page_file_sha256 values joined with \\n in page order; names_root is the same over the 480 names_sha256 values. Two roots, because one of them (names) survives a different JSON serializer.", "cursor_check": "each chain entry's page_file name is '-.json', so chain continuity is checkable from the recorded file names alone." }, "how_to_re_derive": [ "1. GET the same list endpoint with page size 100 and no credentials: the response object carries `servers` and `metadata.nextCursor`.", "2. For each page: body_bytes = the raw response body; page_file_sha256 = sha256 of the body re-serialized exactly as json.dump(json.loads(body)) in Python (default separators ', ' and ': ', ensure_ascii=True). names_sha256 = sha256 of the sorted `name@version` strings for that page joined with '\\n' (no trailing newline) - this one is whitespace- and serializer-independent.", "3. Order pages by the cursor chain: page 1 has no incoming cursor; every later page's incoming cursor must equal the previous page's outgoing cursor; the walk ends when a page carries no nextCursor.", "4. Compare your chain_root_sha256 / names_root_sha256 with the values here. If they match, you have reproduced this same population at your moment; if they differ, compare page by page to find where the registry changed, and publish that page rather than a new total.", "5. If a page answers non-2xx or times out, retry at the SAME cursor; never treat an error body as an end-of-cursor. That single mistake is how a first-page slice gets quoted as a population." ], "chain": { "pages": 480, "full_pages": 479, "last_page_records": 44, "first_page": 1, "last_page": 480, "whole_chain": "/v1/registry-walk?pages=1", "one_page": "/v1/registry-walk?page=N for N in 1..480; anything outside that range is refused with 404 and a named reason, never an empty 200", "arithmetic": "479 full pages x 100 + last page 44 = 47944" }, "what_this_does_not_say": [ "It is a count of ROWS at one moment, not of active servers, live endpoints or operators, and not a market size.", "It says nothing about whether any listed server works: this walk read metadata only, contacted no MCP server and sent no credential.", "The raw bodies are not published - only two hashes per page - so recomputing the totals means re-running the walk, not re-deriving these hashes from published bytes.", "Another operator measured 38,977 rows / 24,321 with a remote on 2026-10-04. That is a different window from a method we have not inspected; it is not contradicted here and this block does not correct it.", "Our own conformance census covers a 109-row slice of this population and carries that slice's selection bias; /v1/census serves it and says so there too." ], "contribute": "If your walk disagrees, POST /v1/contribute with kind=discrepancy, the page number, and your page hash - a published number is never silently replaced, and the disagreement is stored with its evidence.", "analytics": { "served_as": "https://penny-surface-contract.penny-mcamp.workers.dev/v1/stats/summary", "what": "the compact scoreboard for this origin: per-day requests, the self (x-penny-self: 1) vs non-self split per route family, and per published ?ref= label, with an absent day or label reported as null rather than 0", "full_readout": "https://penny-surface-contract.penny-mcamp.workers.dev/v1/stats", "how_to_discount_us": "only the nonSelf figures describe anyone other than us, and the marker is a declaration, not a verified identity" }, "free": "Free and unauthenticated. No signup, no key, no payment, no tracking parameter required." }