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Python: Add OTEL trace headers on requests to MCP HTTP Streamable Tools #1566

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Python: Add OTEL trace headers on requests to MCP HTTP Streamable Tools #1566

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69d51d7
Add OTEL trace headers on request
tonybaloney Oct 20, 2025
b2c9234
Merge branch 'main' into tracing_mcp_http
tonybaloney Oct 20, 2025
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8 changes: 8 additions & 0 deletions python/packages/core/agent_framework/_mcp.py
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@
from mcp.shared.context import RequestContext
from mcp.shared.exceptions import McpError
from mcp.shared.session import RequestResponder
from opentelemetry.trace import get_current_span
from pydantic import BaseModel, create_model

from ._tools import AIFunction, HostedMCPSpecificApproval
Expand Down Expand Up @@ -810,6 +811,7 @@ def __init__(
terminate_on_close: bool | None = None,
chat_client: "ChatClientProtocol | None" = None,
additional_properties: dict[str, Any] | None = None,
include_traceparent: bool = False,
**kwargs: Any,
) -> None:
"""Initialize the MCP streamable HTTP tool.
Expand Down Expand Up @@ -843,6 +845,7 @@ def __init__(
sse_read_timeout: The timeout for reading from the SSE stream.
terminate_on_close: Close the transport when the MCP client is terminated.
chat_client: The chat client to use for sampling.
include_traceparent: Whether to include the traceparent header in requests.
kwargs: Any extra arguments to pass to the SSE client.
"""
super().__init__(
Expand All @@ -863,6 +866,7 @@ def __init__(
self.sse_read_timeout = sse_read_timeout
self.terminate_on_close = terminate_on_close
self._client_kwargs = kwargs
self._include_traceparent = include_traceparent

def get_mcp_client(self) -> _AsyncGeneratorContextManager[Any, None]:
"""Get an MCP streamable HTTP client.
Expand All @@ -883,6 +887,10 @@ def get_mcp_client(self) -> _AsyncGeneratorContextManager[Any, None]:
args["terminate_on_close"] = self.terminate_on_close
if self._client_kwargs:
args.update(self._client_kwargs)
if self._include_traceparent:
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I think it’s better to build this around per-request dynamic headers, not mutate the tool's static dict. Capture the static headers once in MCPStreamableHTTPTool, then pass an optional dynamic_headers callable down into streamablehttp_client / StreamableHTTPTransport. The callable can pull the current span, make sure the context is valid, derive the sampled flag, and return {"traceparent": ...} only when it should be sent. We can then have _prepare_request_headers merge that callable's output on every POST so each RPC carries the active span while the static headers stay untouched. That then handles a possible KeyError when no headers were supplied and keeps the trace flag accurate instead of hardcoding 01.

span_ctx = get_current_span().get_span_context()
args["headers"]["traceparent"] = \
f"00-{span_ctx.trace_id:032x}-{span_ctx.span_id:016x}-01"
return streamablehttp_client(**args)


Expand Down
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