refactor: avoid double JSON parsing (modelcontextprotocol#1917)

Kludex · web-flow · commit ae7793efd6dc · 2026-01-21T13:07:05.000+01:00
diff --git a/src/mcp/server/auth/handlers/register.py b/src/mcp/server/auth/handlers/register.py
@@ -32,10 +32,8 @@ class RegistrationHandler:
     async def handle(self, request: Request) -> Response:
         # Implements dynamic client registration as defined in https://datatracker.ietf.org/doc/html/rfc7591#section-3.1
         try:
-            # Parse request body as JSON
-            # TODO(Marcelo): This is unnecessary. We should use `request.body()`.
-            body = await request.json()
-            client_metadata = OAuthClientMetadata.model_validate(body)
+            body = await request.body()
+            client_metadata = OAuthClientMetadata.model_validate_json(body)
 
             # Scope validation is handled below
         except ValidationError as validation_error:
diff --git a/src/mcp/server/fastmcp/server.py b/src/mcp/server/fastmcp/server.py
@@ -114,7 +114,7 @@ def __init__(
         website_url: str | None = None,
         icons: list[Icon] | None = None,
         version: str | None = None,
-        auth_server_provider: (OAuthAuthorizationServerProvider[Any, Any, Any] | None) = None,
+        auth_server_provider: OAuthAuthorizationServerProvider[Any, Any, Any] | None = None,
         token_verifier: TokenVerifier | None = None,
         *,
         tools: list[Tool] | None = None,
@@ -123,7 +123,7 @@ def __init__(
         warn_on_duplicate_resources: bool = True,
         warn_on_duplicate_tools: bool = True,
         warn_on_duplicate_prompts: bool = True,
-        lifespan: (Callable[[FastMCP[LifespanResultT]], AbstractAsyncContextManager[LifespanResultT]] | None) = None,
+        lifespan: Callable[[FastMCP[LifespanResultT]], AbstractAsyncContextManager[LifespanResultT]] | None = None,
         auth: AuthSettings | None = None,
     ):
         self.settings = Settings(
