feat: Implement SEP-986: Tool Name Guidance

src/mcp/types.py

@@ -1,7 +1,7 @@
 from collections.abc import Callable
 from typing import Annotated, Any, Generic, Literal, TypeAlias, TypeVar
 
-from pydantic import BaseModel, ConfigDict, Field, FileUrl, RootModel
+from pydantic import BaseModel, ConfigDict, Field, FileUrl, RootModel, StringConstraints
 from pydantic.networks import AnyUrl, UrlConstraints
 from typing_extensions import deprecated
 
@@ -199,7 +199,7 @@ class EmptyResult(Result):
 class BaseMetadata(BaseModel):
     """Base class for entities with name and optional title fields."""
 
-    name: str
+    name: Annotated[str, StringConstraints(min_length=1, max_length=128, pattern=r"^[A-Za-z0-9_.-]+$")]
     """The programmatic name of the entity."""
 
     title: str | None = None
@@ -891,6 +891,11 @@ class Tool(BaseMetadata):
     """
     model_config = ConfigDict(extra="allow")
 
+    """
+    See [MCP specification](https://modelcontextprotocol.io/specification/draft/server/tools#tool-names)
+    for more information on tool naming conventions.
+    """
+
 
 class ListToolsResult(PaginatedResult):
     """The server's response to a tools/list request from the client."""

tests/test_types.py

@@ -9,6 +9,7 @@
     InitializeRequestParams,
     JSONRPCMessage,
     JSONRPCRequest,
+    Tool,
 )
 
 
@@ -56,3 +57,18 @@ async def test_method_initialization():
     assert initialize_request.method == "initialize", "method should be set to 'initialize'"
     assert initialize_request.params is not None
     assert initialize_request.params.protocolVersion == LATEST_PROTOCOL_VERSION
+
+
+@pytest.mark.parametrize(
+    "name",
+    [
+        "getUser",
+        "DATA_EXPORT_v2",
+        "admin.tools.list",
+        "a",
+        "Z9_.-",
+        "x" * 128,  # max length
+    ],
+)
+def test_tool_allows_valid_names(name: str) -> None:
+    Tool(name=name, inputSchema={"type": "object"})