MCP spec conformance: 3 requirement(s) violated (via @hasmcp/mcp-spec-test) — spec 2025-11-25

An automated MCP protocol conformance sweep using `@hasmcp/mcp-spec-test` found that the public AWS MCP gateway (reached via `mcp-proxy-for-aws`, at `https://aws-mcp.us-east-1.api.aws/mcp`) rejects a version-less `tools/list` request with a JSON-RPC `-32602 Invalid request parameters` error instead of serving it on the default revision, and that a stock official-SDK client cannot complete a handshake or list tools against it. This was tested against spec revision **2025-11-25**, one of two revisions this server negotiates; against the newer revision (2026-07-28) the same server fails 9 requirements, including a `server/discover` failure not seen here — see the separate issue filed for that revision, since the results differ noticeably by revision.

## Conformance report

MCP 2025-11-25 conformance report
target uvx mcp-proxy-for-aws@1.6.4 https://aws-mcp.us-east-1.api.aws/mcp
transport stdio
supported 2026-07-28, 2025-11-25

FAILED (3) — the server deviates from the spec here

Version negotiation
✗ a request with no version at all is served on the default
a version-less tools/list must be served, not refused: {"code":-32602,"message":"Invalid request parameters","data":""}

Official SDK interop
✗ a stock official-SDK client completes the handshake
MCP error -32602: Invalid request parameters
✗ a stock official-SDK client can list tools
MCP error -32602: Invalid request parameters

NOT VERIFIED (14) — skipped; a skip is not a pass

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

Version negotiation
– initialize returns the schema-required fields
– the handshake settles on the revision under test
no session — initialize returned no result (status 0)

Official SDK interop
– the handshake settles on a revision inside the supported window
target refused a fresh initialize: {"code":-32602,"message":"Invalid request parameters","data":""} — so which revision it negotiates could not be established

PASSED (3)

server/discover
✓ the suite is reading a schema that matches the features it selected

Version negotiation
✓ 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

Summary
3 passed 3 failed 14 not verified
20 cases applied, in 13426ms

Verdict: not conformant — 3 requirements violated.

## How to reproduce

**With Docker:**
```
docker pull hasmcp/mcp-spec-test:latest
docker run --rm hasmcp/mcp-spec-test --spec-version 2025-11-25 -c "uvx mcp-proxy-for-aws@1.6.4 https://aws-mcp.us-east-1.api.aws/mcp"
```
(or, if that image lacks a manifest for 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 --spec-version 2025-11-25 -c "uvx mcp-proxy-for-aws@1.6.4 https://aws-mcp.us-east-1.api.aws/mcp"`)

**Without Docker (npx):**
```
npx @hasmcp/mcp-spec-test@latest --spec-version 2025-11-25 -c "uvx mcp-proxy-for-aws@1.6.4 https://aws-mcp.us-east-1.api.aws/mcp"
```

Note: no AWS credentials are configured in the test environment; the same `-32602` on the version-less `tools/list` and handshake calls also occurs when signing is skipped entirely (`uvx mcp-proxy-for-aws@1.6.4 --skip-auth https://aws-mcp.us-east-1.api.aws/mcp`), so this does not appear to be a missing-credentials artifact.

---
This issue was generated by an automated MCP conformance sweep. Please feel free to close it if it doesn't apply or turns out to be an environment-specific artifact.

Run the reported @hasmcp/mcp-spec-test command against the mcp-proxy-for-aws endpoint, first with Docker or npx and then with --skip-auth. Compare the handshake and version-less tools/list results with the 2025-11-25 conformance report; done means the three failed requirements pass without introducing the separately tracked failures for the newer revision.

Written by the indexing model from the issue text.