MCP spec conformance: 6 requirement(s) violated (via @hasmcp/mcp-spec-test) — spec 2026-07-28

[hasmcp-dev]

When a client negotiates the newer 2026-07-28 MCP spec revision, hyperbrowser-mcp returns -32601 Method not found for server/discover, so a client that relies on that method (rather than a bare initialize) can't determine the server's capabilities at all — every downstream capability check the suite tries then has to be skipped as unverifiable. Note that the server is fully conformant against the older 2025-11-25 revision (0 failures there), so this is specifically about the newer revision's server/discover method not being implemented.

Conformance report

MCP 2026-07-28 conformance report

Verdict: not conformant — 6 requirements violated.

Target	npx hyperbrowser-mcp dummy-key-1234
Transport	stdio
Revision tested	2026-07-28
Revisions supported	2026-07-28, 2025-11-25
Passed	8
Failed	6
Not verified	22
Cases applied	36
Duration	10908ms
Generated	2026-08-24T09:28:39.696Z
Tool	@hasmcp/mcp-spec-test 0.1.1

Failed (6)

the server deviates from the spec here

server/discover

• server/discover is answered without a session or handshake
  server/discover unexpected JSON-RPC error: {"code":-32601,"message":"Method not found"}
• server/discover advertises the versions the server can serve
  server/discover unexpected JSON-RPC error: {"code":-32601,"message":"Method not found"}
• server/discover is a CacheableResult with usable cache hints
  server/discover unexpected JSON-RPC error: {"code":-32601,"message":"Method not found"}
• server/discover reports server identity and capabilities
  server/discover unexpected JSON-RPC error: {"code":-32601,"message":"Method not found"}
• server/discover is stable across calls within its own TTL
  server/discover unexpected JSON-RPC error: {"code":-32601,"message":"Method not found"}
• server/discover advertises a revision this suite supports
  server/discover unexpected JSON-RPC error: {"code":-32601,"message":"Method not found"}

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 an error: {"code":-32601,"message":"Method not found"}
• tools/call on an unknown tool is an error, not a crash
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}
• tools/call returns a schema-conformant CallToolResult
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}
• prompts/list returns schema-conformant prompts
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}
• prompts/get returns messages with a role and content
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}
• resources/list returns schema-conformant resources
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}
• resources/templates/list returns schema-conformant templates
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}
• resources/read returns contents for every sampled resource
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}
• resources/read on an unknown uri is an error
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}
• following nextCursor terminates and does not repeat a page
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}
• an invalid pagination cursor is rejected (SHOULD)
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}

Version negotiation

• a version declared in _meta is accepted
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}
• an unsupported version is rejected with the supported list
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}
• clientInfo is optional (SHOULD, not MUST)
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}

Result envelope

• every result carries the required resultType
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}
• cacheable list results carry the schema-required cache hints
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}
• results identify the server in _meta
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}
• a client on an older version receives no newer-revision fields
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}

subscriptions/listen

• subscriptions/listen acknowledges only the opted-in notification types
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}
• the acknowledgment carries the subscription id for correlation
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}
• a listen requesting no notification types is not a subscription to everything
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}
• a cancelled subscription ends with a conformant teardown result, if it sends one
  cannot determine what the target supports — server/discover returned an error: {"code":-32601,"message":"Method not found"}

Passed (8)

checked and conformant

server/discover

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

Version negotiation

• a request with no version at all is served on the default

Result envelope

• schema sanity: the envelope fields match the features selected

Official SDK interop

• the official SDK does not yet implement the newest revision
• a stock official-SDK client completes the handshake
• the handshake settles on a revision inside the supported window
• a stock official-SDK client can list tools

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 hyperbrowser-mcp dummy-key-1234" --spec-version 2026-07-28

Without Docker (npx):

npx @hasmcp/mcp-spec-test@latest -c "npx hyperbrowser-mcp dummy-key-1234" --spec-version 2026-07-28

---

This issue was filed as part of an automated MCP conformance sweep. Note the server is fully conformant against the older 2025-11-25 spec revision, so this is only about server/discover support for the newer revision, which the spec makes optional/recommended in some contexts — feel free to close if this is intentionally out of scope for your server's target revision.