⚗️ Trace to tool attempt

Signed-off-by: Evaline Ju <69598118+evaline-ju@users.noreply.github.com>

Author: evaline-ju

a2a/weather_service/src/weather_service/agent.py

@@ -119,7 +119,18 @@ async def execute(self, context: RequestContext, event_queue: EventQueue):
         # Test MCP connection first
         logger.info(f'Attempting to connect to MCP server at: {os.getenv("MCP_URL", "http://localhost:8000/sse")}')
 
-        mcpclient = get_mcpclient()
+        # Extract current trace context for propagation to Envoy/MCP
+        traceparent = None
+        root_span = get_root_span()
+        if root_span and root_span.is_recording():
+            span_context = root_span.get_span_context()
+            if span_context.is_valid:
+                # Format traceparent according to W3C Trace Context spec
+                # Format: version-trace_id-span_id-trace_flags
+                traceparent = f"00-{format(span_context.trace_id, '032x')}-{format(span_context.span_id, '016x')}-{format(span_context.trace_flags, '02x')}"
+                logger.info(f'Propagating trace context to MCP: {traceparent}')
+
+        mcpclient = get_mcpclient(traceparent=traceparent)
 
         # Try to get tools to verify connection
         try:

a2a/weather_service/src/weather_service/graph.py

@@ -12,12 +12,27 @@
 class ExtendedMessagesState(MessagesState):
      final_answer: str = ""
 
-def get_mcpclient():
-    return MultiServerMCPClient({
-        "math": {
-            "url": os.getenv("MCP_URL", "http://localhost:8000/mcp"),
-            "transport": os.getenv("MCP_TRANSPORT", "streamable_http"),
+def get_mcpclient(traceparent: str | None = None):
+    """
+    Create an MCP client with optional trace context propagation.
+
+    Args:
+        traceparent: W3C Trace Context traceparent header value
+                    Format: "00-{trace-id}-{parent-id}-{trace-flags}"
+    """
+    server_config = {
+        "url": os.getenv("MCP_URL", "http://localhost:8000/mcp"),
+        "transport": os.getenv("MCP_TRANSPORT", "streamable_http"),
+    }
+
+    # Add traceparent header if provided for distributed tracing through Envoy
+    if traceparent:
+        server_config["headers"] = {
+            "traceparent": traceparent
         }
+
+    return MultiServerMCPClient({
+        "math": server_config
     })
 
 async def get_graph(client) -> StateGraph: