diff --git a/packages/mcp-client/package.json b/packages/mcp-client/package.json
index 0a3cc15c28..60345eec90 100644
--- a/packages/mcp-client/package.json
+++ b/packages/mcp-client/package.json
@@ -34,7 +34,7 @@
 		"prepare": "pnpm run build",
 		"test": "vitest run",
 		"check": "tsc",
-		"agent": "tsx cli.ts"
+		"cli": "tsx cli.ts"
 	},
 	"files": [
 		"src",
diff --git a/packages/mcp-client/src/McpClient.ts b/packages/mcp-client/src/McpClient.ts
index a3d45479ed..04fe2b86e0 100644
--- a/packages/mcp-client/src/McpClient.ts
+++ b/packages/mcp-client/src/McpClient.ts
@@ -160,13 +160,18 @@ export class McpClient {
 			for (const toolCall of delta.tool_calls ?? []) {
 				// aggregating chunks into an encoded arguments JSON object
 				if (!finalToolCalls[toolCall.index]) {
+					/// first chunk of the tool call
 					finalToolCalls[toolCall.index] = toolCall;
-				}
-				if (finalToolCalls[toolCall.index].function.arguments === undefined) {
-					finalToolCalls[toolCall.index].function.arguments = "";
-				}
-				if (toolCall.function.arguments) {
-					finalToolCalls[toolCall.index].function.arguments += toolCall.function.arguments;
+
+					/// ensure .function.arguments is always a string
+					if (finalToolCalls[toolCall.index].function.arguments === undefined) {
+						finalToolCalls[toolCall.index].function.arguments = "";
+					}
+				} else {
+					/// any subsequent chunk to the same tool call
+					if (toolCall.function.arguments) {
+						finalToolCalls[toolCall.index].function.arguments += toolCall.function.arguments;
+					}
 				}
 			}
 			if (opts.exitIfFirstChunkNoTool && numOfChunks <= 2 && Object.keys(finalToolCalls).length === 0) {