MCP spec conformance: 10 requirement(s) violated (via @hasmcp/mcp-spec-test) — spec 2026-07-28

[hasmcp-dev]

Running the black-box @hasmcp/mcp-spec-test conformance suite against wigolo (via npx -y wigolo, the bare stdio-server invocation documented in mcp.json/the installation guide) with the client requesting the newest 2026-07-28 revision shows the server not answering server/discover or initialize at all — the suite reports the underlying process as exited, and the official-SDK client sees "Connection closed" — which blocks verification of 22 further checks. We manually confirmed the process itself stays alive when stdin is held open, but it doesn't respond to an initialize request sent over stdio within a reasonable window either, so this doesn't look like a fluke of the test harness (the process not literally crashing, but also not implementing the MCP handshake it advertises) — though we can't fully rule out that this specific package needs some one-time setup (wigolo init, which downloads a ~1.5GB browser engine + models) before the bare npx -y wigolo server is usable, and the README doesn't make that a hard prerequisite for mcp.json's documented invocation.

Conformance report

MCP 2026-07-28 conformance report

Verdict: not conformant — 10 requirements violated.

Target	npx -y wigolo
Transport	stdio
Revision tested	2026-07-28
Revisions supported	2026-07-28, 2025-11-25
Passed	4
Failed	10
Not verified	22
Cases applied	36
Duration	12233ms
Generated	2026-08-24T14:24:27.119Z
Tool	@hasmcp/mcp-spec-test 0.1.1

Failed (10)

the server deviates from the spec here

server/discover

• server/discover is answered without a session or handshake
  expected 200, got 0: {"_raw":"server exited"}

  0 !== 200

• server/discover advertises the versions the server can serve
  Cannot read properties of undefined (reading 'supportedVersions')

• server/discover is a CacheableResult with usable cache hints
  Cannot read properties of undefined (reading 'ttlMs')

• server/discover reports server identity and capabilities
  Cannot read properties of undefined (reading 'capabilities')

• server/discover is stable across calls within its own TTL
  Cannot read properties of undefined (reading 'supportedVersions')

• server/discover advertises a revision this suite supports
  Cannot read properties of undefined (reading 'supportedVersions')

Version negotiation

• a request with no version at all is served on the default
  a version-less request must be served, got 0: {"_raw":"server exited"}

  0 !== 200

Official SDK interop

• a stock official-SDK client completes the handshake
  MCP error -32000: Connection closed
• the handshake settles on a revision inside the supported window
  initialize must return a protocolVersion, got undefined
• a stock official-SDK client can list tools
  MCP error -32000: Connection closed

Not verified (22)

skipped; a skip is not a pass

Capability methods

• tools/list returns schema-conformant tools
  cannot determine what the target supports — server/discover returned no result (status 0)
• tools/call on an unknown tool is an error, not a crash
  cannot determine what the target supports — server/discover returned no result (status 0)
• tools/call returns a schema-conformant CallToolResult
  cannot determine what the target supports — server/discover returned no result (status 0)
• prompts/list returns schema-conformant prompts
  cannot determine what the target supports — server/discover returned no result (status 0)
• prompts/get returns messages with a role and content
  cannot determine what the target supports — server/discover returned no result (status 0)
• resources/list returns schema-conformant resources
  cannot determine what the target supports — server/discover returned no result (status 0)
• resources/templates/list returns schema-conformant templates
  cannot determine what the target supports — server/discover returned no result (status 0)
• resources/read returns contents for every sampled resource
  cannot determine what the target supports — server/discover returned no result (status 0)
• resources/read on an unknown uri is an error
  cannot determine what the target supports — server/discover returned no result (status 0)
• following nextCursor terminates and does not repeat a page
  cannot determine what the target supports — server/discover returned no result (status 0)
• an invalid pagination cursor is rejected (SHOULD)
  cannot determine what the target supports — server/discover returned no result (status 0)

Version negotiation

• a version declared in _meta is accepted
  cannot determine what the target supports — server/discover returned no result (status 0)
• an unsupported version is rejected with the supported list
  cannot determine what the target supports — server/discover returned no result (status 0)
• clientInfo is optional (SHOULD, not MUST)
  cannot determine what the target supports — server/discover returned no result (status 0)

Result envelope

• every result carries the required resultType
  cannot determine what the target supports — server/discover returned no result (status 0)
• cacheable list results carry the schema-required cache hints
  cannot determine what the target supports — server/discover returned no result (status 0)
• results identify the server in _meta
  cannot determine what the target supports — server/discover returned no result (status 0)
• a client on an older version receives no newer-revision fields
  cannot determine what the target supports — server/discover returned no result (status 0)

subscriptions/listen

• subscriptions/listen acknowledges only the opted-in notification types
  cannot determine what the target supports — server/discover returned no result (status 0)
• the acknowledgment carries the subscription id for correlation
  cannot determine what the target supports — server/discover returned no result (status 0)
• a listen requesting no notification types is not a subscription to everything
  cannot determine what the target supports — server/discover returned no result (status 0)
• a cancelled subscription ends with a conformant teardown result, if it sends one
  cannot determine what the target supports — server/discover returned no result (status 0)

Passed (4)

checked and conformant

server/discover

• the suite is reading a schema that matches the features it selected

Result envelope

• schema sanity: the envelope fields match the features selected

Official SDK interop

• the official SDK does not yet implement the newest revision

subscriptions/listen

• schema sanity: SubscriptionsListenResult requires _meta and resultType

How to reproduce

With Docker:

docker pull hasmcp/mcp-spec-test:latest
docker run --rm hasmcp/mcp-spec-test -c "npx -y wigolo" --spec-version 2026-07-28

(on Apple Silicon / arm64 hosts, add --platform linux/amd64; the published image currently only ships an amd64 manifest but runs fine under emulation)

Without Docker (npx):

npx @hasmcp/mcp-spec-test@latest -c "npx -y wigolo" --spec-version 2026-07-28

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This report was generated by an automated MCP conformance sweep across public MCP server repos. If this is tied to wigolo needing init to run first (which our black-box test can't do, since mcp.json documents the bare invocation), or is otherwise not applicable, feel free to close it — no offense taken.