fix: Utilize pydantic constraints

Author: vincent0426

src/mcp/types.py

@@ -1,8 +1,7 @@
-import re
 from collections.abc import Callable
 from typing import Annotated, Any, Generic, Literal, TypeAlias, TypeVar
 
-from pydantic import BaseModel, ConfigDict, Field, FileUrl, RootModel, field_validator
+from pydantic import BaseModel, ConfigDict, Field, FileUrl, RootModel, StringConstraints
 from pydantic.networks import AnyUrl, UrlConstraints
 from typing_extensions import deprecated
 
@@ -40,10 +39,6 @@
 RequestId = Annotated[int, Field(strict=True)] | str
 AnyFunction: TypeAlias = Callable[..., Any]
 
-# Tool name validation pattern (ASCII letters, digits, underscore, dash, dot)
-# Pattern ensures entire string contains only valid characters by using ^ and $ anchors
-TOOL_NAME_PATTERN = re.compile(r"^[A-Za-z0-9_.-]+$")
-
 
 class RequestParams(BaseModel):
     class Meta(BaseModel):
@@ -204,7 +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
@@ -896,17 +891,6 @@ class Tool(BaseMetadata):
     """
     model_config = ConfigDict(extra="allow")
 
-    @field_validator("name")
-    @classmethod
-    def _validate_tool_name(cls, value: str) -> str:
-        if not (1 <= len(value) <= 128):
-            raise ValueError(f"Invalid tool name length: {len(value)}. Tool name must be between 1 and 128 characters.")
-
-        if not TOOL_NAME_PATTERN.fullmatch(value):
-            raise ValueError("Invalid tool name characters. Allowed: A-Z, a-z, 0-9, underscore (_), dash (-), dot (.).")
-
-        return value
-
     """
     See [MCP specification](https://modelcontextprotocol.io/specification/draft/server/tools#tool-names)
     for more information on tool naming conventions.

tests/test_types.py

@@ -72,22 +72,3 @@ async def test_method_initialization():
 )
 def test_tool_allows_valid_names(name: str) -> None:
     Tool(name=name, inputSchema={"type": "object"})
-
-
-@pytest.mark.parametrize(
-    ("name", "expected"),
-    [
-        ("", "Invalid tool name length: 0. Tool name must be between 1 and 128 characters."),
-        ("x" * 129, "Invalid tool name length: 129. Tool name must be between 1 and 128 characters."),
-        ("has space", "Invalid tool name characters. Allowed: A-Z, a-z, 0-9, underscore (_), dash (-), dot (.)."),
-        ("comma,name", "Invalid tool name characters. Allowed: A-Z, a-z, 0-9, underscore (_), dash (-), dot (.)."),
-        ("not/allowed", "Invalid tool name characters. Allowed: A-Z, a-z, 0-9, underscore (_), dash (-), dot (.)."),
-        ("name@", "Invalid tool name characters. Allowed: A-Z, a-z, 0-9, underscore (_), dash (-), dot (.)."),
-        ("name#", "Invalid tool name characters. Allowed: A-Z, a-z, 0-9, underscore (_), dash (-), dot (.)."),
-        ("name$", "Invalid tool name characters. Allowed: A-Z, a-z, 0-9, underscore (_), dash (-), dot (.)."),
-    ],
-)
-def test_tool_rejects_invalid_names(name: str, expected: str) -> None:
-    with pytest.raises(ValueError) as exc_info:
-        Tool(name=name, inputSchema={"type": "object"})
-    assert expected in str(exc_info.value)