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

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_instances_by_security_group(security_group_name: str) -> str:
+        """
+        Get instances associated with a specific security group.
+
+        :param security_group_name: The name of the security group to filter instances by.
+        """
+        return (
+            f"Find all compute instances 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_prompts.py

@@ -0,0 +1,29 @@
+from openstack_mcp_server.prompts import register_prompt
+
+
+def test_get_instances_by_security_group_prompt_registered():
+    """Test that the prompt is registered with the MCP instance."""
+    from unittest.mock import MagicMock
+
+    mcp = MagicMock()
+    register_prompt(mcp)
+    mcp.prompt.assert_called()
+
+
+def test_get_instances_by_security_group_prompt_content():
+    """Test that the prompt returns expected content."""
+    from fastmcp import FastMCP
+
+    mcp = FastMCP("test")
+    register_prompt(mcp)
+
+    prompts = mcp._prompt_manager._prompts
+    assert "get_instances_by_security_group" in prompts
+
+    prompt_obj = prompts["get_instances_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