get_cwan_routes throws Error: 'Destinations' on segments with blackhole routes

Description

get_cwan_routes fails with an unhandled error (Error calling tool 'get_cwan_routes': 'Destinations') when called against a segment whose route table contains a blackhole route with target: null, while working correctly for segments with only active/propagated routes.

Environment

• awslabs.aws-network-mcp-server version: 0.0.13 (via uvx awslabs.aws-network-mcp-server@latest)
• MCP client: Claude Code
• Region: eu-west-1

Steps to reproduce

1. Call get_all_cwan_routes(core_network_id="<core-network-id>", cloudwan_region="eu-west-1", profile_name="<profile>") and find a segment whose routes include an entry shaped like:
   json复制

   {"destination": "0.0.0.0/0", "target": null, "type": "static", "state": "blackhole"}

   (confirmed via get_all_cwan_routes in this account — the segment in question has exactly two such routes, 0.0.0.0/0 and ::/0, both blackhole with target: null.)
2. Call get_cwan_routes(core_network_id="<core-network-id>", region="eu-west-1", segment="<that-segment-name>", profile_name="<profile>") on the same segment.
3. Compare against a segment with only active/propagated routes (works fine), and a segment with zero routes at all (also works fine, returns "No network routes found with the given parameters.").

Actual behavior

Error calling tool 'get_cwan_routes': 'Destinations'

Confirmed via two data points: a segment with blackhole/null-target routes fails; a segment with zero routes succeeds with a clean "no routes" message; multiple segments with active/propagated routes all succeed normally. The differentiator appears to be specifically the presence of a blackhole route with a null target, not segment isolation or route count.

Expected behavior

The tool should return blackhole routes the same way get_all_cwan_routes does (with target: null, state: "blackhole") rather than throwing an unhandled error.

Additional context

The error message (bare 'Destinations') suggests the per-segment code path does a route['Destinations'] or similar lookup on the raw AWS API response shape, and something about blackhole/no-target route entries doesn't match the expected shape — while get_all_cwan_routes clearly already handles this shape correctly (it returns target: null cleanly), suggesting the two tools use different parsing logic for the same underlying GetNetworkRoutes API response.