Handle ollama's deviation from the OpenAI tool streaming spec

Author: julien-c

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) {