fix: include mcp_tool_permissions server ids in allowed mcp servers (#22311)

when a key/team/end-user has mcp_tool_permissions for a server but that
server is not in mcp_servers, the server was excluded from the allowed
list — making the tool permissions useless.

now we union the keys from mcp_tool_permissions into the allowed server
set alongside direct servers and access group servers.

fixes #21954

litellm/proxy/_experimental/mcp_server/auth/user_api_key_auth_mcp.py

@@ -649,8 +649,13 @@ class MCPRequestHandler:
                 )
             )
 
-            # Combine both lists
-            all_servers = direct_mcp_servers + access_group_servers
+            # servers referenced in tool permissions should also be accessible
+            tool_perm_servers = list(
+                (key_object_permission.mcp_tool_permissions or {}).keys()
+            )
+
+            # Combine all lists
+            all_servers = direct_mcp_servers + access_group_servers + tool_perm_servers
             return list(set(all_servers))
         except Exception as e:
             verbose_logger.warning(
@@ -686,8 +691,13 @@ class MCPRequestHandler:
                 )
             )
 
-            # Combine both lists
-            all_servers = direct_mcp_servers + access_group_servers
+            # servers referenced in tool permissions should also be accessible
+            tool_perm_servers = list(
+                (object_permissions.mcp_tool_permissions or {}).keys()
+            )
+
+            # Combine all lists
+            all_servers = direct_mcp_servers + access_group_servers + tool_perm_servers
             return list(set(all_servers))
         except Exception as e:
             verbose_logger.warning(
@@ -737,8 +747,6 @@ class MCPRequestHandler:
             # Get direct MCP servers
             direct_mcp_servers = end_user_obj.object_permission.mcp_servers or []
 
-
-
             # Get MCP servers from access groups
             access_group_servers = (
                 await MCPRequestHandler._get_mcp_servers_from_access_groups(
@@ -746,8 +754,13 @@ class MCPRequestHandler:
                 )
             )
 
-            # Combine both lists
-            all_servers = direct_mcp_servers + access_group_servers
+            # servers referenced in tool permissions should also be accessible
+            tool_perm_servers = list(
+                (end_user_obj.object_permission.mcp_tool_permissions or {}).keys()
+            )
+
+            # Combine all lists
+            all_servers = direct_mcp_servers + access_group_servers + tool_perm_servers
             return list(set(all_servers))
         except Exception as e:
             verbose_logger.warning(

tests/test_litellm/proxy/_experimental/mcp_server/auth/test_user_api_key_auth_mcp.py

@@ -1738,3 +1738,34 @@ class TestAgentMCPPermissions:
                         user_api_key_auth=user_api_key_auth,
                     )
                     assert sorted(result) == ["tool_a", "tool_b"]
+
+
+@pytest.mark.asyncio
+async def test_tool_permission_servers_included_in_allowed_servers():
+    """
+    Servers listed only in mcp_tool_permissions (not in mcp_servers)
+    should still be accessible.
+
+    Regression test for https://github.com/BerriAI/litellm/issues/21954
+    """
+    perm = MagicMock()
+    perm.mcp_servers = []
+    perm.mcp_access_groups = []
+    perm.mcp_tool_permissions = {"server_id_123": ["tool_a", "tool_b"]}
+
+    user_api_key_auth = UserAPIKeyAuth(
+        api_key="test-key",
+        user_id="test-user",
+    )
+
+    with patch.object(
+        MCPRequestHandler, "_get_key_object_permission", return_value=perm
+    ), patch.object(
+        MCPRequestHandler, "_get_mcp_servers_from_access_groups",
+        new_callable=AsyncMock,
+        return_value=[],
+    ):
+        result = await MCPRequestHandler._get_allowed_mcp_servers_for_key(
+            user_api_key_auth=user_api_key_auth,
+        )
+        assert "server_id_123" in result