No OTEL Context propagation in ADK

[g3force]

There seems to be an issue with Google ADK: The OTEL trace context is not propagated to other remote services, especially:

• MCP Servers
• AI Gateway (model router)

Propagation works from Agent to sub agents (a2a remote agents) already.

Related: google/adk-python#4285

To reproduce: Use https://github.com/agentic-layer/showcase-news (Tilt) to spin up the agents, gateway, mcp tool and LGTM stack.
Observe that traces are created for agent gateway, agent, sub agent, ai gateway and mcp tool, but the two later ones are not part of the main trace (they are root traces):

[g3force]

See also: agentic-layer/agent-template-adk#5

[g3force]

Seems to work with MCP (now). Using FastMCP 3.0.0b2.

[g3force]

This is working fine with MSAF, so until this got fixed in ADK, better use MSAF instead.