Fixed Code Escaping for MCP Tools

Author: robertheadley

src/core/tools/useMcpToolTool.ts

@@ -44,27 +44,63 @@ export async function useMcpToolTool(
 
 			if (mcp_arguments) {
 				try {
+					// First try to parse as JSON directly
 					parsedArguments = JSON.parse(mcp_arguments)
 				} catch (error) {
-					cline.consecutiveMistakeCount++
-					cline.recordToolError("use_mcp_tool")
-					await cline.say("error", `Roo tried to use ${tool_name} with an invalid JSON argument. Retrying...`)
-
-					pushToolResult(
-						formatResponse.toolError(formatResponse.invalidMcpToolArgumentError(server_name, tool_name)),
-					)
-
-					return
+					// If direct parsing fails, try to handle it as a raw string that might need escaping
+					try {
+						// Check if it looks like a JSON object already (starts with { or [)
+						const trimmed = mcp_arguments.trim()
+						if (
+							(trimmed.startsWith("{") && trimmed.endsWith("}")) ||
+							(trimmed.startsWith("[") && trimmed.endsWith("]"))
+						) {
+							// If it looks like JSON but couldn't be parsed, then it's truly invalid
+							cline.consecutiveMistakeCount++
+							cline.recordToolError("use_mcp_tool")
+							await cline.say(
+								"error",
+								`Roo tried to use ${tool_name} with an invalid JSON argument. Retrying...`,
+							)
+
+							pushToolResult(
+								formatResponse.toolError(
+									formatResponse.invalidMcpToolArgumentError(server_name, tool_name),
+								),
+							)
+							return
+						}
+
+						// Otherwise, handle it as a raw string input - automatically place it in a properly escaped JSON object
+						// This assumes the MCP tool expects an object with an 'input_data' field
+						parsedArguments = {
+							input_data: mcp_arguments,
+						}
+
+						console.log("Auto-escaped code for MCP tool:", tool_name)
+					} catch (nestedError) {
+						cline.consecutiveMistakeCount++
+						cline.recordToolError("use_mcp_tool")
+						await cline.say("error", `Failed to process arguments for ${tool_name}. Please try again.`)
+
+						pushToolResult(
+							formatResponse.toolError(
+								formatResponse.invalidMcpToolArgumentError(server_name, tool_name),
+							),
+						)
+						return
+					}
 				}
 			}
 
 			cline.consecutiveMistakeCount = 0
 
+			// Create the approval message with the properly formatted arguments
 			const completeMessage = JSON.stringify({
 				type: "use_mcp_tool",
 				serverName: server_name,
 				toolName: tool_name,
-				arguments: mcp_arguments,
+				arguments: parsedArguments ? JSON.stringify(parsedArguments) : mcp_arguments,
 			} satisfies ClineAskUseMcpServer)
 
 			const didApprove = await askApproval("use_mcp_server", completeMessage)

src/test-mcp-escaping.js

@@ -0,0 +1,76 @@
+// Test script for MCP code escaping
+// This script tests the code escaping functionality for MCP tools
+// It simulates the behavior of useMcpToolTool.ts with different types of input
+
+function testMcpEscaping(input, description) {
+  console.log(`\n=== Testing ${description} ===`);
+  console.log("Input:", input);
+  
+  try {
+    // First try to parse as JSON directly (normal behavior)
+    const parsed = JSON.parse(input);
+    console.log("✅ Successfully parsed as JSON:", parsed);
+    return parsed;
+  } catch (error) {
+    console.log("❌ Failed to parse as JSON, trying fallback handling...");
+    
+    try {
+      // Check if it looks like a JSON object already (starts with { or [)
+      const trimmed = input.trim();
+      if (
+        (trimmed.startsWith("{") && trimmed.endsWith("}")) ||
+        (trimmed.startsWith("[") && trimmed.endsWith("]"))
+      ) {
+        // If it looks like JSON but couldn't be parsed, then it's truly invalid
+        console.log("❌ Input appears to be invalid JSON");
+        return null;
+      }
+
+      // Otherwise, handle it as a raw string input - automatically place it in a properly escaped JSON object
+      const parsedArguments = {
+        input_data: input,
+      };
+      console.log("✅ Handled as raw string input:", parsedArguments);
+      return parsedArguments;
+    } catch (nestedError) {
+      console.log("❌ Failed to process arguments:", nestedError);
+      return null;
+    }
+  }
+}
+
+// Test cases
+console.log("TESTING MCP CODE ESCAPING");
+
+// Test 1: Valid JSON
+testMcpEscaping('{"name": "test", "value": 123}', "Valid JSON");
+
+// Test 2: Invalid JSON
+testMcpEscaping('{name: "test", value: 123}', "Invalid JSON");
+
+// Test 3: LaTeX code with backslashes and special characters
+testMcpEscaping(`\\stepcounter{fragenummer}
+\\arabic{fragenummer}. & \\multicolumn{1}{|p{12cm}|}{\\raggedright #1 } & \\ifthenelse{#2=1}{{
+\\color{blue}{X}
+}}{} & \\ifthenelse{#2=1}{}{
+\\color{blue}{X}
+}`, "LaTeX code with special characters");
+
+// Test 4: Python code with indentation, quotes and backslashes
+testMcpEscaping(`def process_string(s):
+    # Handle escape sequences
+    s = s.replace('\\n', '\\\\n')
+    s = s.replace('\\t', '\\\\t')
+    
+    # Handle quotes
+    s = s.replace('"', '\\"')
+    s = s.replace("'", "\\'")
+    
+    return f"Processed: {s}"
+
+print(process_string("Hello\\nWorld"))`, "Python code with quotes and backslashes");
+
+// Test 5: Plain text
+testMcpEscaping("This is just plain text without any special formatting", "Plain text");
+
+console.log("\nAll tests completed!");