Should CallToolResult.structuredContent be a JsonArray?

Given that CallToolResult.content is a List<PromptMessageContent>, I'd expect structuredContent to be a JsonArray, but it's a JsonObject.

I can wrap the results in an object with something like

           CallToolResult(
               content = jsonResult.toPromptMessageContent(), // Converts array to list of TextContent
               structuredContent = buildJsonObject { put("results", jsonResult) }
           )

However, when using the MCP Inspector, I get this warning:

⚠ No text block matches structured content

Which makes me think this implementation might be incompatible with some clients. A workaround can be:

            val wrapperResult = buildJsonObject { put("results", jsonResult) }
            CallToolResult(
                content = listOf(TextContent(wrapperResult.toString())),
                structuredContent = wrapperResult
            )

But passing a single item to content doesn't look optimal.

Is this the recommended approach or am I missing something? Thank you!

Start in kotlin-sdk-core/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/types.kt at the CallToolResult definition around line 1210, then compare its structuredContent type with the MCP result schema and the MCP Inspector warning. Done means the expected representation and client compatibility are established, with the implementation or issue documentation aligned accordingly.