MCP spec conformance: 1 requirement(s) violated (via @hasmcp/mcp-spec-test) — spec 2025-11-25

Running the @hasmcp/mcp-spec-test conformance suite against npx -y n8n-mcp, tested against protocol revision 2025-11-25, shows a single violation: a client that offers 2025-11-25 during the handshake is answered with 2025-03-26 instead — a revision outside the window (2026-07-28, 2025-11-25) the server itself advertises as supported. This is a much narrower issue than the one found under revision 2026-07-28 (filed separately, with 7 violations there, mostly due to a missing server/discover method). This may be intentional backward-compatibility behavior rather than a bug — please feel free to close if not applicable.

Conformance report

MCP 2025-11-25 conformance report

Verdict: not conformant — 1 requirement violated.

Target	npx -y n8n-mcp
Transport	stdio
Revision tested	2025-11-25
Revisions supported	2026-07-28, 2025-11-25
Passed	6
Failed	1
Not verified	13
Cases applied	20
Duration	5700ms
Generated	2026-08-24T05:27:08.524Z
Tool	@hasmcp/mcp-spec-test 0.1.1

Failed (1)

the server deviates from the spec here

Official SDK interop

• the handshake settles on a revision inside the supported window a client offering 2025-11-25 was answered with 2025-03-26, outside the supported window (2026-07-28, 2025-11-25)

Not verified (13)

skipped; a skip is not a pass

Capability methods

• tools/list returns schema-conformant tools cannot determine what the target supports — server negotiated 2025-03-26, not the 2025-11-25 under test
• tools/call on an unknown tool is an error, not a crash cannot determine what the target supports — server negotiated 2025-03-26, not the 2025-11-25 under test
• tools/call returns a schema-conformant CallToolResult cannot determine what the target supports — server negotiated 2025-03-26, not the 2025-11-25 under test
• prompts/list returns schema-conformant prompts cannot determine what the target supports — server negotiated 2025-03-26, not the 2025-11-25 under test
• prompts/get returns messages with a role and content cannot determine what the target supports — server negotiated 2025-03-26, not the 2025-11-25 under test
• resources/list returns schema-conformant resources cannot determine what the target supports — server negotiated 2025-03-26, not the 2025-11-25 under test
• resources/templates/list returns schema-conformant templates cannot determine what the target supports — server negotiated 2025-03-26, not the 2025-11-25 under test
• resources/read returns contents for every sampled resource cannot determine what the target supports — server negotiated 2025-03-26, not the 2025-11-25 under test
• resources/read on an unknown uri is an error cannot determine what the target supports — server negotiated 2025-03-26, not the 2025-11-25 under test
• following nextCursor terminates and does not repeat a page cannot determine what the target supports — server negotiated 2025-03-26, not the 2025-11-25 under test
• an invalid pagination cursor is rejected (SHOULD) cannot determine what the target supports — server negotiated 2025-03-26, not the 2025-11-25 under test

Version negotiation

• initialize returns the schema-required fields no session — server negotiated 2025-03-26, not the 2025-11-25 under test
• the handshake settles on the revision under test no session — server negotiated 2025-03-26, not the 2025-11-25 under test

Passed (6)

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
• an unsupported version offered at the handshake is refused or downgraded, not echoed

Official SDK interop

• the official SDK does not yet implement the newest revision
• a stock official-SDK client completes the handshake
• a stock official-SDK client can list tools

How to reproduce

With Docker:

docker pull hasmcp/mcp-spec-test:latest
docker run --rm hasmcp/mcp-spec-test -c "npx -y n8n-mcp" --spec-version 2025-11-25

(or, if that image can't run on your platform: git clone https://github.com/hasmcp/mcp-spec-test && cd mcp-spec-test && docker build -t mcp-spec-test . && docker run --rm mcp-spec-test -c "npx -y n8n-mcp" --spec-version 2025-11-25)

Without Docker (npx):

npx @hasmcp/mcp-spec-test@latest -c "npx -y n8n-mcp" --spec-version 2025-11-25

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This issue was filed as part of an automated conformance sweep of public MCP servers using @hasmcp/mcp-spec-test. If this turns out to be a false positive specific to the test environment (missing credentials/dependencies, etc.), please feel free to close it.