diff --git a/packages-ext/telemetry/src/utils/stream-text.ts b/packages-ext/telemetry/src/utils/stream-text.ts
index 32a5b19..899239d 100644
--- a/packages-ext/telemetry/src/utils/stream-text.ts
+++ b/packages-ext/telemetry/src/utils/stream-text.ts
@@ -164,7 +164,6 @@ export const streamText = (options: WithUnknown<WithTelemetry<StreamTextOptions>
             // https://platform.openai.com/docs/guides/function-calling?api-mode=chat&lang=javascript#streaming
             for (const toolCall of choice.delta.tool_calls) {
               const { index } = toolCall
-              const toolName = toolCall.function.name!
 
               if (!tool_calls.at(index)) {
                 tool_calls[index] = {
@@ -174,7 +173,7 @@ export const streamText = (options: WithUnknown<WithTelemetry<StreamTextOptions>
                     arguments: toolCall.function.arguments!,
                   },
                 }
-                pushEvent({ toolCallId: toolCall.id, toolName, type: 'tool-call-streaming-start' })
+                pushEvent({ toolCallId: toolCall.id, toolName: toolCall.function.name!, type: 'tool-call-streaming-start' })
               }
               else {
                 tool_calls[index].function.arguments! += toolCall.function.arguments
diff --git a/packages/stream-text/src/index.ts b/packages/stream-text/src/index.ts
index fa0cec7..275b4be 100644
--- a/packages/stream-text/src/index.ts
+++ b/packages/stream-text/src/index.ts
@@ -146,7 +146,6 @@ export const streamText = (options: WithUnknown<StreamTextOptions>): StreamTextR
             // https://platform.openai.com/docs/guides/function-calling?api-mode=chat&lang=javascript#streaming
             for (const toolCall of choice.delta.tool_calls) {
               const { index } = toolCall
-              const toolName = toolCall.function.name!
 
               if (!tool_calls.at(index)) {
                 tool_calls[index] = {
@@ -156,7 +155,7 @@ export const streamText = (options: WithUnknown<StreamTextOptions>): StreamTextR
                     arguments: toolCall.function.arguments!,
                   },
                 }
-                pushEvent({ toolCallId: toolCall.id, toolName, type: 'tool-call-streaming-start' })
+                pushEvent({ toolCallId: toolCall.id, toolName: toolCall.function.name!, type: 'tool-call-streaming-start' })
               }
               else {
                 tool_calls[index].function.arguments! += toolCall.function.arguments