fix(mcp): balance host alert tool suggestions

apps/api/src/services/mcp_tool_registry.py

@@ -171,9 +171,13 @@ class MCPToolRegistry:
         """
         suggested: list[RegisteredTool] = []
         labels = incident_labels or {}
+        # namespace alone is only routing context.  Requiring a concrete
+        # workload/node locator prevents host alerts such as HostErrorLogFlood
+        # from being misrouted into Kubernetes tools just because an upstream
+        # bridge added namespace="infra".
         has_k8s_locator = any(
             labels.get(key)
-            for key in ("deployment", "pod", "node", "namespace", "container")
+            for key in ("deployment", "pod", "node", "container")
         )
 
         # 依優先度排序後篩選
@@ -195,8 +199,10 @@ class MCPToolRegistry:
             # 但允許多個工具覆蓋同一維度（例如 D1 需要 kubectl_describe + kubectl_events）
             suggested.append(reg)
 
-        # 取前 max_tools 個
-        result = suggested[:max_tools]
+        # 取前 max_tools 個；同一 provider 先給半數上限，避免單一 MCP
+        # provider 擠滿整個 8D 預算，讓 SignOz/Prometheus/Sentry 這類側證
+        # 有機會和主診斷工具一起進入調查。
+        result = _select_provider_balanced_tools(suggested, max_tools)
 
         logger.debug(
             "mcp_registry_suggest_tools",
@@ -219,6 +225,37 @@ class MCPToolRegistry:
         return len(self._tools)
 
 
+def _select_provider_balanced_tools(
+    tools: list[RegisteredTool],
+    max_tools: int,
+) -> list[RegisteredTool]:
+    if max_tools <= 0:
+        return []
+
+    provider_soft_cap = max(2, max_tools // 2)
+    selected: list[RegisteredTool] = []
+    deferred: list[RegisteredTool] = []
+    provider_counts: dict[str, int] = {}
+
+    for reg in tools:
+        if len(selected) >= max_tools:
+            break
+        provider_name = reg.provider.name
+        count = provider_counts.get(provider_name, 0)
+        if count >= provider_soft_cap:
+            deferred.append(reg)
+            continue
+        selected.append(reg)
+        provider_counts[provider_name] = count + 1
+
+    for reg in deferred:
+        if len(selected) >= max_tools:
+            break
+        selected.append(reg)
+
+    return selected
+
+
 # ─────────────────────────────────────────────────────────────────────────────
 # 工具自動分類（根據 tool name 推斷感官維度）
 # ─────────────────────────────────────────────────────────────────────────────

apps/api/tests/test_mcp_tool_registry.py

@@ -282,6 +282,16 @@ class TestSuggestTools:
         assert "kubectl_describe" in names
         assert "prometheus_query" in names
 
+    def test_namespace_only_non_kube_alert_does_not_get_k8s_tool(self):
+        registry = self._registry_with_tools()
+        tools = registry.suggest_tools(
+            alertname="HostErrorLogFlood",
+            incident_labels={"namespace": "infra"},
+        )
+        names = [t.tool.name for t in tools]
+        assert "kubectl_describe" not in names
+        assert "prometheus_query" in names
+
     def test_empty_alertname_gets_generic_only(self):
         registry = self._registry_with_tools()
         tools = registry.suggest_tools(alertname="")
@@ -342,10 +352,19 @@ class TestSuggestTools:
         registry = MCPToolRegistry()
         ssh_provider = _StubProvider(
             "ssh_host",
-            ["ssh_diagnose", "ssh_get_top_processes", "ssh_get_container_logs"],
+            [
+                "ssh_diagnose",
+                "ssh_get_top_processes",
+                "ssh_get_container_logs",
+                "ssh_get_container_status",
+                "ssh_get_service_status",
+                "ssh_check_port",
+            ],
         )
+        k8s_provider = _StubProvider("kubernetes", ["kubectl_describe"])
         signoz_provider = _StubProvider("signoz", ["query_logs"])
         prometheus_provider = _StubProvider("prometheus", ["prometheus_query"])
+        await registry.register_provider(k8s_provider)
         await registry.register_provider(ssh_provider)
         await registry.register_provider(signoz_provider)
         await registry.register_provider(prometheus_provider)
@@ -358,7 +377,7 @@ class TestSuggestTools:
                 "sensor_ip": "192.168.0.188",
                 "host": "192.168.0.188",
             },
-            max_tools=10,
+            max_tools=8,
         )
         names = [reg.tool.name for reg in tools]
 
@@ -366,6 +385,7 @@ class TestSuggestTools:
         assert "ssh_get_top_processes" in names
         assert "query_logs" in names
         assert "prometheus_query" in names
+        assert "kubectl_describe" not in names
 
     def test_get_all_tools_returns_all(self):
         registry = MCPToolRegistry()