Adding description field to the FastMCP get_prompt method (#614)

Co-authored-by: ihrpr <inna@anthropic.com>

tests/server/fastmcp/test_server.py

@@ -982,6 +982,46 @@ class TestServerPrompts:
             assert isinstance(content, TextContent)
             assert content.text == "Hello, World!"
 
+    @pytest.mark.anyio
+    async def test_get_prompt_with_description(self):
+        """Test getting a prompt through MCP protocol."""
+        mcp = FastMCP()
+
+        @mcp.prompt(description="Test prompt description")
+        def fn(name: str) -> str:
+            return f"Hello, {name}!"
+
+        async with client_session(mcp._mcp_server) as client:
+            result = await client.get_prompt("fn", {"name": "World"})
+            assert result.description == "Test prompt description"
+
+    @pytest.mark.anyio
+    async def test_get_prompt_without_description(self):
+        """Test getting a prompt without description returns empty string."""
+        mcp = FastMCP()
+
+        @mcp.prompt()
+        def fn(name: str) -> str:
+            return f"Hello, {name}!"
+
+        async with client_session(mcp._mcp_server) as client:
+            result = await client.get_prompt("fn", {"name": "World"})
+            assert result.description == ""
+
+    @pytest.mark.anyio
+    async def test_get_prompt_with_docstring_description(self):
+        """Test prompt uses docstring as description when not explicitly provided."""
+        mcp = FastMCP()
+
+        @mcp.prompt()
+        def fn(name: str) -> str:
+            """This is the function docstring."""
+            return f"Hello, {name}!"
+
+        async with client_session(mcp._mcp_server) as client:
+            result = await client.get_prompt("fn", {"name": "World"})
+            assert result.description == "This is the function docstring."
+
     @pytest.mark.anyio
     async def test_get_prompt_with_resource(self):
         """Test getting a prompt that returns resource content."""