THE FOMITE

The MCP Observatory / who watches the watchers

We published an MCP server. Two dozen robots showed up to inspect it.

The moment a server lands in the MCP registry, an invisible ecosystem wakes up: crawlers that grade it, monitor its uptime, verify its ownership, diff its tools, and check whether it wants paying. Almost nobody has documented these. The Fomite can, because it is the fresh server they came to inspect — so it sees exactly who knocks, how fast, and what they look at.

32Watchers seen
3Kinds
549Their requests
86MCP calls logged
3x402 knocks

The watchers

Every client below is a piece of infrastructure whose job is to watch otherMCP servers. We identify them by User-Agent; unverified until forward/reverse DNS confirms them.

WatcherKindWhat it doesrobotsRequestsFound us in
SentinelOracle MCP watcherMCP liveness monitor (heavy poller).never-read2551.7 h
mcpbeat MCP watcherMCP-server liveness monitor.never-read1092.6 h
AgentGrade agent directoryAgent security-research crawler.never-read243.8 h
agent-tools.cloud agent directoryAgent-tools directory crawler.never-read144.8 h
aisec-registry MCP watcherAI-security MCP registry scanner.never-read129.4 h
MCPWatch MCP watcherLongitudinal MCP security research.never-read104.8 h
reliability-bureau-spike MCP watcherReliability monitor.never-read810.2 h
ProofBench MCP watcherMCP registry health / benchmark.never-read826 min
mcpgrade-probe MCP watcherMCP-server grading probe.never-read78.2 h
spanly-enrich agent directoryEnrichment crawler.never-read78.7 h
402explorer agent paymentProbes whether a server requires x402 payment.never-read74.3 h
VerifyMCP MCP watcherMCP verification service (probe + owners bot).never-read61.0 h
zerm-tool-census MCP watcherMCP tool census crawler.never-read66.2 h
SmitheryBot MCP watcherSmithery MCP directory crawler (registry cascade).never-read625 min
mcp-drift-monitor MCP watcherRead-only tool-definition drift observer.never-read61.4 h
ProwlBot agent directoryDirectory crawler.never-read510.1 h
AgentIndexBot agent directoryAgent registry directory crawler.compliant55.0 h
api-forge-mcp-index MCP watcherMCP index crawler.insufficient-data32.5 h
rootz-mcp-registry-prober MCP watcherMCP registry prober.insufficient-data310.3 h
MCPWitness MCP watcherMCP health probe.insufficient-data37.5 h
measure-mcp-schema MCP watcherMCP schema measurement.insufficient-data34.5 h
x402-observatory agent paymentx402 payment-ecosystem research collector.insufficient-data37.3 h
HUNT-Bot agent directoryDiscovery engine.insufficient-data20 min
domains-distillery agent directoryDomain crawler.insufficient-data21.8 h
SaSameAgentAudit MCP watcherAgent audit probe.insufficient-data28.5 h
lastseen MCP watcherIntrospection-only schema probe.insufficient-data26.3 h
understory agent directoryCertificate-transparency research crawler.insufficient-data20 min
skillex-enrichment agent directoryEnrichment crawler.insufficient-data15.0 h
AgentReputationBot agent directoryAgent reputation scanner.insufficient-data14.2 h
AIVE-MCP-EndpointProbe MCP watcherMCP endpoint probe.insufficient-data18.8 h
catalog-health MCP watcherMCP catalog health probe.insufficient-data14.3 h
CertSignalBot agent directoryCertificate-signal monitor.insufficient-data14.3 h

How fast they found us

The Fomite's server entered the official MCP registry at 2026-08-19 23:00:00 UTC. Here is how long each watcher took to arrive after that — a rough read on which parts of the ecosystem are fast and which are slow.

OrderWatcherFirst seen (UTC)After publish
1HUNT-Bot2026-08-19 21:040 min
2understory2026-08-19 21:060 min
3SmitheryBot2026-08-19 23:2425 min
4ProofBench2026-08-19 23:2626 min
5VerifyMCP2026-08-20 00:001.0 h
6mcp-drift-monitor2026-08-20 00:251.4 h
7SentinelOracle2026-08-20 00:441.7 h
8domains-distillery2026-08-20 00:461.8 h
9api-forge-mcp-index2026-08-20 01:282.5 h
10mcpbeat2026-08-20 01:342.6 h
11AgentGrade2026-08-20 02:463.8 h
12AgentReputationBot2026-08-20 03:124.2 h
13CertSignalBot2026-08-20 03:154.3 h
14402explorer2026-08-20 03:174.3 h
15catalog-health2026-08-20 03:194.3 h
16measure-mcp-schema2026-08-20 03:314.5 h
17MCPWatch2026-08-20 03:474.8 h
18agent-tools.cloud2026-08-20 03:484.8 h
19AgentIndexBot2026-08-20 03:585.0 h
20skillex-enrichment2026-08-20 03:585.0 h
21zerm-tool-census2026-08-20 05:096.2 h
22lastseen2026-08-20 05:206.3 h
23x402-observatory2026-08-20 06:157.3 h
24MCPWitness2026-08-20 06:307.5 h
25mcpgrade-probe2026-08-20 07:138.2 h
26SaSameAgentAudit2026-08-20 07:298.5 h
27spanly-enrich2026-08-20 07:448.7 h
28AIVE-MCP-EndpointProbe2026-08-20 07:498.8 h
29aisec-registry2026-08-20 08:239.4 h
30ProwlBot2026-08-20 09:0610.1 h
31reliability-bureau-spike2026-08-20 09:1310.2 h
32rootz-mcp-registry-prober2026-08-20 09:1710.3 h

What they looked at

Every watcher reads our tools/list. So we turned the telescope around and recorded their reading: which MCP methods each one calls. The observed become the observatory.

MCP methodCallsDistinct clients
initialize308
tools/list298
notifications/initialized265
tools/call11

Tools actually invoked (not just introspected)

ToolCalls
fomite_census1

Per watcher

WatcherMethods it called
curlinitialize×2 tools/list×1 tools/call×1
mcpbeattools/list×6 initialize×6 notifications/initialized×6
nodetools/list×2 notifications/initialized×2 initialize×2
rootz-mcp-registry-probernotifications/initialized×1 tools/list×1 initialize×1
SentinelOraclenotifications/initialized×16 tools/list×16 initialize×16
unidentifiedinitialize×3 tools/list×3 notifications/initialized×1

The x402 experiment

Some of these crawlers exist to find MCP servers that charge for access, over the emerging x402 agent-payment protocol. So we set a trap for the trap-finders: https://thefomite.com/api/x402/premium answers with a real HTTP 402 payment challenge. No funds are ever taken — it is a testnet challenge with a zero address, disclosed as research, and any payment header at all gets free access. The only thing we collect is who knocked.

3Knocks (402s served)
1Payment attempts
1Distinct clients
Who knockedTimesTried to pay
curl31

Method: /methodology. Discovery latency is measured from the registry-publish time above and clamped at zero for anything that found us by another channel first. The x402 endpoint never collects funds.