Prints cache token usage in tracing

Author: Workshop Participant

src/strands/telemetry/tracer.py

@@ -257,6 +257,8 @@ def end_model_invoke_span(
         attributes: Dict[str, AttributeValue] = {
             "gen_ai.usage.prompt_tokens": usage["inputTokens"],
             "gen_ai.usage.input_tokens": usage["inputTokens"],
+            "gen_ai.usage.cache_read_input_tokens": usage.get("cacheReadInputTokens", 0),
+            "gen_ai.usage.cache_write_input_tokens": usage.get("cacheWriteInputTokens", 0),
             "gen_ai.usage.completion_tokens": usage["outputTokens"],
             "gen_ai.usage.output_tokens": usage["outputTokens"],
             "gen_ai.usage.total_tokens": usage["totalTokens"],
@@ -490,6 +492,8 @@ def end_agent_span(
                         "gen_ai.usage.input_tokens": accumulated_usage["inputTokens"],
                         "gen_ai.usage.output_tokens": accumulated_usage["outputTokens"],
                         "gen_ai.usage.total_tokens": accumulated_usage["totalTokens"],
+                        "gen_ai.usage.cache_read_input_tokens": accumulated_usage["cacheReadInputTokens"],
+                        "gen_ai.usage.cache_write_input_tokens": accumulated_usage["cacheWriteInputTokens"],
                     }
                 )