feat: add get_instances_by_security_group prompt (#103)

* feat: add get_instances_by_security_group prompt

Add a prompt that guides LLM to find compute instances associated
with a specific security group using existing tools.

Closes #101

* refactor: rename prompt from get_instances to get_servers

Align naming with compute_tools convention (server over instance)
as suggested in code review.

* style: align prompt test structure with tools test convention

Wrap test functions in TestPrompts class and move imports to
module level, matching the pattern used in tests/tools/.

* refactor: rename test file to test_network_prompts.py

Align test file naming with tools convention (e.g. test_network_tools.py)
since security group is a network domain feature.

Author: paikend

src/openstack_mcp_server/prompts/__init__.py

@@ -0,0 +1,26 @@
+from fastmcp import FastMCP
+
+
+def register_prompt(mcp: FastMCP):
+    """
+    Register Openstack MCP prompts.
+    """
+
+    @mcp.prompt()
+    def get_servers_by_security_group(security_group_name: str) -> str:
+        """
+        Get servers associated with a specific security group.
+
+        :param security_group_name: The name of the security group to filter servers by.
+        """
+        return (
+            f"Find all compute servers that have the security group "
+            f"'{security_group_name}' attached.\n\n"
+            f"Steps:\n"
+            f"1. Call get_servers to list all servers.\n"
+            f"2. Check each server's security_groups field.\n"
+            f"3. Return only the servers where security_groups contains "
+            f"an entry with name '{security_group_name}'.\n"
+            f"4. For each matching server, show the server name, ID, "
+            f"status, and the full list of its security groups."
+        )

src/openstack_mcp_server/server.py

@@ -2,6 +2,7 @@
 from fastmcp.server.middleware.error_handling import ErrorHandlingMiddleware
 from fastmcp.server.middleware.logging import LoggingMiddleware
 
+from openstack_mcp_server.prompts import register_prompt
 from openstack_mcp_server.tools import register_tool
 
 
@@ -13,7 +14,7 @@ def serve(transport: str, **kwargs):
 
     register_tool(mcp)
     # resister_resources(mcp)
-    # register_prompt(mcp)
+    register_prompt(mcp)
 
     # Add middlewares
     mcp.add_middleware(ErrorHandlingMiddleware())

tests/prompts/test_network_prompts.py

@@ -0,0 +1,31 @@
+from unittest.mock import MagicMock
+
+from fastmcp import FastMCP
+
+from openstack_mcp_server.prompts import register_prompt
+
+
+class TestPrompts:
+    """Test cases for MCP prompts."""
+
+    def test_get_servers_by_security_group_prompt_registered(self):
+        """Test that the prompt is registered with the MCP instance."""
+        mcp = MagicMock()
+        register_prompt(mcp)
+        mcp.prompt.assert_called()
+
+    def test_get_servers_by_security_group_prompt_content(self):
+        """Test that the prompt returns expected content."""
+        mcp = FastMCP("test")
+        register_prompt(mcp)
+
+        prompts = mcp._prompt_manager._prompts
+        assert "get_servers_by_security_group" in prompts
+
+        prompt_obj = prompts["get_servers_by_security_group"]
+        assert prompt_obj.fn is not None
+
+        result = prompt_obj.fn(security_group_name="my-sg")
+        assert "my-sg" in result
+        assert "get_servers" in result
+        assert "security_groups" in result