Merge pull request #35 from 0xeb/fix/issue-33-interop-stdio

fix(client+stdio): normalize JSON-RPC envelopes and notification handling

Author: 0xeb

include/fastmcpp/client/client.hpp

@@ -285,11 +285,13 @@ class Client
             response = invoke_request();
         }
 
+        const auto& response_body = unwrap_rpc_result(response);
+
         // Optional server-side progress events
-        if (options.progress_handler && response.contains("progress") &&
-            response["progress"].is_array())
+        if (options.progress_handler && response_body.contains("progress") &&
+            response_body["progress"].is_array())
         {
-            for (const auto& p : response["progress"])
+            for (const auto& p : response_body["progress"])
             {
                 float value = p.value("progress", 0.0f);
                 std::optional<float> total = std::nullopt;
@@ -301,9 +303,9 @@ class Client
         }
 
         // Notification forwarding (sampling/elicitation/roots) if provided by server
-        if (response.contains("notifications") && response["notifications"].is_array())
+        if (response_body.contains("notifications") && response_body["notifications"].is_array())
         {
-            for (const auto& n : response["notifications"])
+            for (const auto& n : response_body["notifications"])
             {
                 if (!n.contains("method"))
                     continue;
@@ -385,16 +387,18 @@ class Client
     TaskStatus get_task_status(const std::string& task_id)
     {
         fastmcpp::Json response = call("tasks/get", {{"taskId", task_id}});
+        const auto& body = unwrap_rpc_result(response);
         TaskStatus status;
-        from_json(response, status);
+        from_json(body, status);
         return status;
     }
 
     /// Retrieve raw task result via MCP 'tasks/result' (tool/prompt/resource specific).
     /// Callers are responsible for parsing into appropriate result type.
     fastmcpp::Json get_task_result_raw(const std::string& task_id)
     {
-        return call("tasks/result", {{"taskId", task_id}});
+        fastmcpp::Json response = call("tasks/result", {{"taskId", task_id}});
+        return unwrap_rpc_result(response);
     }
 
     /// List tasks via MCP 'tasks/list'. Returns raw JSON as provided by server.
@@ -406,16 +410,18 @@ class Client
             params["cursor"] = *cursor;
         if (limit > 0)
             params["limit"] = limit;
-        return call("tasks/list", params);
+        fastmcpp::Json response = call("tasks/list", params);
+        return unwrap_rpc_result(response);
     }
 
     /// Cancel a background task via MCP 'tasks/cancel'. Returns final task status.
     /// @throws fastmcpp::Error if task does not exist or server returns error
     TaskStatus cancel_task(const std::string& task_id)
     {
         fastmcpp::Json response = call("tasks/cancel", {{"taskId", task_id}});
+        const auto& body = unwrap_rpc_result(response);
         TaskStatus status;
-        from_json(response, status);
+        from_json(body, status);
         return status;
     }
 
@@ -705,9 +711,10 @@ class Client
     void poll_notifications()
     {
         auto response = call("notifications/poll", fastmcpp::Json::object());
-        if (!response.contains("notifications") || !response["notifications"].is_array())
+        const auto& body = unwrap_rpc_result(response);
+        if (!body.contains("notifications") || !body["notifications"].is_array())
             return;
-        for (const auto& n : response["notifications"])
+        for (const auto& n : body["notifications"])
         {
             if (!n.contains("method"))
                 continue;
@@ -916,36 +923,66 @@ class Client
         return value;
     }
 
+    const fastmcpp::Json& unwrap_rpc_result(const fastmcpp::Json& response)
+    {
+        if (!response.is_object())
+            return response;
+
+        if (response.contains("error"))
+        {
+            if (response["error"].is_object())
+            {
+                const auto& error = response["error"];
+                std::string message = error.value("message", "Unknown JSON-RPC error");
+                if (error.contains("code") && error["code"].is_number_integer())
+                {
+                    throw fastmcpp::Error("JSON-RPC error (" +
+                                          std::to_string(error["code"].get<int>()) + "): " +
+                                          message);
+                }
+                throw fastmcpp::Error("JSON-RPC error: " + message);
+            }
+            throw fastmcpp::Error("JSON-RPC error: " + response["error"].dump());
+        }
+
+        if (response.contains("result"))
+            return response["result"];
+
+        return response;
+    }
+
     ListToolsResult parse_list_tools_result(const fastmcpp::Json& response)
     {
+        const auto& body = unwrap_rpc_result(response);
         ListToolsResult result;
-        if (response.contains("tools"))
-            for (const auto& t : response["tools"])
+        if (body.contains("tools"))
+            for (const auto& t : body["tools"])
                 result.tools.push_back(t.get<ToolInfo>());
-        if (response.contains("nextCursor"))
-            result.nextCursor = response["nextCursor"].get<std::string>();
-        if (response.contains("_meta"))
-            result._meta = response["_meta"];
+        if (body.contains("nextCursor"))
+            result.nextCursor = body["nextCursor"].get<std::string>();
+        if (body.contains("_meta"))
+            result._meta = body["_meta"];
         return result;
     }
 
     CallToolResult parse_call_tool_result(const fastmcpp::Json& response,
                                           const std::string& tool_name)
     {
+        const auto& body = unwrap_rpc_result(response);
 
         CallToolResult result;
-        result.isError = response.value("isError", false);
+        result.isError = body.value("isError", false);
 
-        if (!response.contains("content"))
+        if (!body.contains("content"))
             throw fastmcpp::ValidationError("tools/call response missing content");
 
-        if (response.contains("content"))
-            for (const auto& c : response["content"])
+        if (body.contains("content"))
+            for (const auto& c : body["content"])
                 result.content.push_back(parse_content_block(c));
 
-        if (response.contains("structuredContent"))
+        if (body.contains("structuredContent"))
         {
-            result.structuredContent = response["structuredContent"];
+            result.structuredContent = body["structuredContent"];
             // Try to provide a convenient data view similar to Python
             auto structured = *result.structuredContent;
             auto it = tool_output_schemas_.find(tool_name);
@@ -1011,31 +1048,33 @@ class Client
             }
         }
 
-        if (response.contains("_meta"))
-            result.meta = response["_meta"];
+        if (body.contains("_meta"))
+            result.meta = body["_meta"];
 
         return result;
     }
 
     ListResourcesResult parse_list_resources_result(const fastmcpp::Json& response)
     {
+        const auto& body = unwrap_rpc_result(response);
         ListResourcesResult result;
-        if (response.contains("resources"))
-            for (const auto& r : response["resources"])
+        if (body.contains("resources"))
+            for (const auto& r : body["resources"])
                 result.resources.push_back(r.get<ResourceInfo>());
-        if (response.contains("nextCursor"))
-            result.nextCursor = response["nextCursor"].get<std::string>();
-        if (response.contains("_meta"))
-            result._meta = response["_meta"];
+        if (body.contains("nextCursor"))
+            result.nextCursor = body["nextCursor"].get<std::string>();
+        if (body.contains("_meta"))
+            result._meta = body["_meta"];
         return result;
     }
 
     ListResourceTemplatesResult parse_list_resource_templates_result(const fastmcpp::Json& response)
     {
+        const auto& body = unwrap_rpc_result(response);
         ListResourceTemplatesResult result;
-        if (response.contains("resourceTemplates"))
+        if (body.contains("resourceTemplates"))
         {
-            for (const auto& r : response["resourceTemplates"])
+            for (const auto& r : body["resourceTemplates"])
             {
                 ResourceTemplate rt;
                 rt.uriTemplate = r.at("uriTemplate").get<std::string>();
@@ -1071,45 +1110,48 @@ class Client
                 result.resourceTemplates.push_back(rt);
             }
         }
-        if (response.contains("nextCursor"))
-            result.nextCursor = response["nextCursor"].get<std::string>();
-        if (response.contains("_meta"))
-            result._meta = response["_meta"];
+        if (body.contains("nextCursor"))
+            result.nextCursor = body["nextCursor"].get<std::string>();
+        if (body.contains("_meta"))
+            result._meta = body["_meta"];
         return result;
     }
 
     ReadResourceResult parse_read_resource_result(const fastmcpp::Json& response)
     {
+        const auto& body = unwrap_rpc_result(response);
         ReadResourceResult result;
-        if (response.contains("contents"))
-            for (const auto& c : response["contents"])
+        if (body.contains("contents"))
+            for (const auto& c : body["contents"])
                 result.contents.push_back(parse_resource_content(c));
-        if (response.contains("_meta"))
-            result._meta = response["_meta"];
+        if (body.contains("_meta"))
+            result._meta = body["_meta"];
         return result;
     }
 
     ListPromptsResult parse_list_prompts_result(const fastmcpp::Json& response)
     {
+        const auto& body = unwrap_rpc_result(response);
         ListPromptsResult result;
-        if (response.contains("prompts"))
-            for (const auto& p : response["prompts"])
+        if (body.contains("prompts"))
+            for (const auto& p : body["prompts"])
                 result.prompts.push_back(p.get<PromptInfo>());
-        if (response.contains("nextCursor"))
-            result.nextCursor = response["nextCursor"].get<std::string>();
-        if (response.contains("_meta"))
-            result._meta = response["_meta"];
+        if (body.contains("nextCursor"))
+            result.nextCursor = body["nextCursor"].get<std::string>();
+        if (body.contains("_meta"))
+            result._meta = body["_meta"];
         return result;
     }
 
     GetPromptResult parse_get_prompt_result(const fastmcpp::Json& response)
     {
+        const auto& body = unwrap_rpc_result(response);
         GetPromptResult result;
-        if (response.contains("description"))
-            result.description = response["description"].get<std::string>();
-        if (response.contains("messages"))
+        if (body.contains("description"))
+            result.description = body["description"].get<std::string>();
+        if (body.contains("messages"))
         {
-            for (const auto& m : response["messages"])
+            for (const auto& m : body["messages"])
             {
                 PromptMessage msg;
                 std::string role = m.at("role").get<std::string>();
@@ -1136,37 +1178,39 @@ class Client
                 result.messages.push_back(msg);
             }
         }
-        if (response.contains("_meta"))
-            result._meta = response["_meta"];
+        if (body.contains("_meta"))
+            result._meta = body["_meta"];
         return result;
     }
 
     CompleteResult parse_complete_result(const fastmcpp::Json& response)
     {
+        const auto& body = unwrap_rpc_result(response);
         CompleteResult result;
-        if (response.contains("completion"))
+        if (body.contains("completion"))
         {
-            const auto& c = response["completion"];
+            const auto& c = body["completion"];
             if (c.contains("values"))
                 for (const auto& v : c["values"])
                     result.completion.values.push_back(v.get<std::string>());
             if (c.contains("total"))
                 result.completion.total = c["total"].get<int>();
             result.completion.hasMore = c.value("hasMore", false);
         }
-        if (response.contains("_meta"))
-            result._meta = response["_meta"];
+        if (body.contains("_meta"))
+            result._meta = body["_meta"];
         return result;
     }
 
     InitializeResult parse_initialize_result(const fastmcpp::Json& response)
     {
+        const auto& body = unwrap_rpc_result(response);
         InitializeResult result;
-        result.protocolVersion = response.value("protocolVersion", "2024-11-05");
+        result.protocolVersion = body.value("protocolVersion", "2024-11-05");
 
-        if (response.contains("capabilities"))
+        if (body.contains("capabilities"))
         {
-            const auto& caps = response["capabilities"];
+            const auto& caps = body["capabilities"];
             if (caps.contains("experimental"))
                 result.capabilities.experimental = caps["experimental"];
             if (caps.contains("logging"))
@@ -1185,17 +1229,17 @@ class Client
                 result.capabilities.extensions = caps["extensions"];
         }
 
-        if (response.contains("serverInfo"))
+        if (body.contains("serverInfo"))
         {
-            result.serverInfo.name = response["serverInfo"].value("name", "unknown");
-            result.serverInfo.version = response["serverInfo"].value("version", "unknown");
+            result.serverInfo.name = body["serverInfo"].value("name", "unknown");
+            result.serverInfo.version = body["serverInfo"].value("version", "unknown");
         }
 
-        if (response.contains("instructions"))
-            result.instructions = response["instructions"].get<std::string>();
+        if (body.contains("instructions"))
+            result.instructions = body["instructions"].get<std::string>();
 
-        if (response.contains("_meta"))
-            result._meta = response["_meta"];
+        if (body.contains("_meta"))
+            result._meta = body["_meta"];
 
         return result;
     }
@@ -1588,18 +1632,19 @@ inline std::shared_ptr<ResourceTask> Client::read_resource_task(const std::strin
         payload["_meta"] = *propagated_meta;
 
     auto response = call("resources/read", payload);
+    const auto& body = unwrap_rpc_result(response);
 
-    if (response.contains("_meta") && response["_meta"].contains("modelcontextprotocol.io/task"))
+    if (body.contains("_meta") && body["_meta"].contains("modelcontextprotocol.io/task"))
     {
-        const auto& task_obj = response["_meta"]["modelcontextprotocol.io/task"];
+        const auto& task_obj = body["_meta"]["modelcontextprotocol.io/task"];
         if (task_obj.contains("taskId"))
         {
             std::string task_id = task_obj["taskId"].get<std::string>();
             return std::make_shared<ResourceTask>(this, std::move(task_id), uri, std::nullopt);
         }
     }
 
-    ReadResourceResult result = parse_read_resource_result(response);
+    ReadResourceResult result = parse_read_resource_result(body);
     return std::make_shared<ResourceTask>(this, std::string{}, uri, std::move(result.contents));
 }
 
@@ -1625,18 +1670,19 @@ Client::get_prompt_task(const std::string& name, const fastmcpp::Json& arguments
         payload["_meta"] = *propagated_meta;
 
     auto response = call("prompts/get", payload);
+    const auto& body = unwrap_rpc_result(response);
 
-    if (response.contains("_meta") && response["_meta"].contains("modelcontextprotocol.io/task"))
+    if (body.contains("_meta") && body["_meta"].contains("modelcontextprotocol.io/task"))
     {
-        const auto& task_obj = response["_meta"]["modelcontextprotocol.io/task"];
+        const auto& task_obj = body["_meta"]["modelcontextprotocol.io/task"];
         if (task_obj.contains("taskId"))
         {
             std::string task_id = task_obj["taskId"].get<std::string>();
             return std::make_shared<PromptTask>(this, std::move(task_id), name, std::nullopt);
         }
     }
 
-    GetPromptResult result = parse_get_prompt_result(response);
+    GetPromptResult result = parse_get_prompt_result(body);
     return std::make_shared<PromptTask>(this, std::string{}, name, std::move(result));
 }