MCP resource not found -32602: Sume is tools-only, so -32601
MCP 2026-07-28 moves resource-not-found from -32002 to -32602. Sume's hosted MCP advertises tools only, so resources/read gets method-not-found -32601.
The MCP 2026-07-28 changelog changes the resource-not-found error code from -32002 to -32602 (Invalid Params). That does not apply to Sume's hosted MCP, because it advertises tools only: an unknown method such as resources/read is answered with method-not-found, code -32601, and the text "MCP method is not supported". Where -32602 does appear is as a catch-all for other request failures.
Spec change read 2026-10-01. Sume behavior is from its MCP server source and the tools and gates docs.
What does Sume advertise?
The initialize result lists a tools capability with listChanged set to false and nothing for resources. A client that wants files should use the asset tools, not resource URIs; the background is in tools vs resources vs prompts.
Which error code comes back for what?
| Situation | Result |
|---|---|
Unknown method, including resources/read | JSON-RPC error -32601 |
| A tool that fails while running | A tool result with isError, not -32602 |
| Other request failures in dispatch | JSON-RPC error -32602 with the error message |
| Empty or oversize legacy batch | HTTP 400 with -32600 |
How should my client handle each?
Treat -32601 on a resources method as "this server has no resources" and stop asking. Read tool failures from the tool result, not from the JSON-RPC error. Only treat -32602 as invalid-request when it arrives as a JSON-RPC error. Other codes are listed in MCP error codes.
Do I need to update for the new resource code?
Only if you talk to servers that expose resources. Against Sume, you will not see a resource-not-found of either code, because there are no resources to miss.
Sources
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