relax validation

examples/servers/simple-auth/mcp_simple_auth/server.py

@@ -214,7 +214,7 @@ async def exchange_authorization_code(
 
         return OAuthToken(
             access_token=mcp_token,
-            token_type="bearer",
+            token_type="Bearer",
             expires_in=3600,
             scope=" ".join(authorization_code.scopes),
         )

src/mcp/shared/auth.py

@@ -1,6 +1,6 @@
 from typing import Any, Literal
 
-from pydantic import AnyHttpUrl, BaseModel, Field
+from pydantic import AnyHttpUrl, BaseModel, Field, field_validator
 
 
 class OAuthToken(BaseModel):
@@ -9,11 +9,20 @@ class OAuthToken(BaseModel):
     """
 
     access_token: str
-    token_type: Literal["bearer"] = "bearer"
+    token_type: Literal["Bearer"] = "Bearer"
     expires_in: int | None = None
     scope: str | None = None
     refresh_token: str | None = None
 
+    @field_validator("token_type", mode="before")
+    @classmethod
+    def normalize_token_type(cls, v: str | None) -> str | None:
+        if isinstance(v, str):
+            # Bearer is title-cased in the spec, so we normalize it
+            # https://datatracker.ietf.org/doc/html/rfc6750#section-4
+            return v.title()
+        return v
+
 
 class InvalidScopeError(Exception):
     def __init__(self, message: str):
@@ -111,13 +120,13 @@ class OAuthMetadata(BaseModel):
     token_endpoint: AnyHttpUrl
     registration_endpoint: AnyHttpUrl | None = None
     scopes_supported: list[str] | None = None
-    response_types_supported: list[Literal["code"]] = ["code"]
+    response_types_supported: list[Literal["code"] | str] = ["code"]
     response_modes_supported: list[Literal["query", "fragment"]] | None = None
     grant_types_supported: (
-        list[Literal["authorization_code", "refresh_token"]] | None
+        list[Literal["authorization_code", "refresh_token"] | str] | None
     ) = None
     token_endpoint_auth_methods_supported: (
-        list[Literal["none", "client_secret_post"]] | None
+        list[Literal["none", "client_secret_post"] | str] | None
     ) = None
     token_endpoint_auth_signing_alg_values_supported: None = None
     service_documentation: AnyHttpUrl | None = None
@@ -126,12 +135,12 @@ class OAuthMetadata(BaseModel):
     op_tos_uri: AnyHttpUrl | None = None
     revocation_endpoint: AnyHttpUrl | None = None
     revocation_endpoint_auth_methods_supported: (
-        list[Literal["client_secret_post"]] | None
+        list[Literal["client_secret_post"] | str] | None
     ) = None
     revocation_endpoint_auth_signing_alg_values_supported: None = None
     introspection_endpoint: AnyHttpUrl | None = None
     introspection_endpoint_auth_methods_supported: (
-        list[Literal["client_secret_post"]] | None
+        list[Literal["client_secret_post"] | str] | None
     ) = None
     introspection_endpoint_auth_signing_alg_values_supported: None = None
-    code_challenge_methods_supported: list[Literal["S256"]] | None = None
+    code_challenge_methods_supported: list[Literal["S256"] | str] | None = None

tests/client/test_auth.py

@@ -91,7 +91,7 @@ def oauth_client_info():
 def oauth_token():
     return OAuthToken(
         access_token="test_access_token",
-        token_type="bearer",
+        token_type="Bearer",
         expires_in=3600,
         refresh_token="test_refresh_token",
         scope="read write",
@@ -143,7 +143,8 @@ def test_generate_code_verifier(self, oauth_provider):
         verifiers = {oauth_provider._generate_code_verifier() for _ in range(10)}
         assert len(verifiers) == 10
 
-    def test_generate_code_challenge(self, oauth_provider):
+    @pytest.mark.anyio
+    async def test_generate_code_challenge(self, oauth_provider):
         """Test PKCE code challenge generation."""
         verifier = "test_code_verifier_123"
         challenge = oauth_provider._generate_code_challenge(verifier)
@@ -161,7 +162,8 @@ def test_generate_code_challenge(self, oauth_provider):
         assert "+" not in challenge
         assert "/" not in challenge
 
-    def test_get_authorization_base_url(self, oauth_provider):
+    @pytest.mark.anyio
+    async def test_get_authorization_base_url(self, oauth_provider):
         """Test authorization base URL extraction."""
         # Test with path
         assert (
@@ -348,11 +350,13 @@ async def test_register_oauth_client_failure(self, oauth_provider):
                         None,
                     )
 
-    def test_has_valid_token_no_token(self, oauth_provider):
+    @pytest.mark.anyio
+    async def test_has_valid_token_no_token(self, oauth_provider):
         """Test token validation with no token."""
         assert not oauth_provider._has_valid_token()
 
-    def test_has_valid_token_valid(self, oauth_provider, oauth_token):
+    @pytest.mark.anyio
+    async def test_has_valid_token_valid(self, oauth_provider, oauth_token):
         """Test token validation with valid token."""
         oauth_provider._current_tokens = oauth_token
         oauth_provider._token_expiry_time = time.time() + 3600  # Future expiry
@@ -370,7 +374,7 @@ async def test_has_valid_token_expired(self, oauth_provider, oauth_token):
     @pytest.mark.anyio
     async def test_validate_token_scopes_no_scope(self, oauth_provider):
         """Test scope validation with no scope returned."""
-        token = OAuthToken(access_token="test", token_type="bearer")
+        token = OAuthToken(access_token="test", token_type="Bearer")
 
         # Should not raise exception
         await oauth_provider._validate_token_scopes(token)
@@ -381,7 +385,7 @@ async def test_validate_token_scopes_valid(self, oauth_provider, client_metadata
         oauth_provider.client_metadata = client_metadata
         token = OAuthToken(
             access_token="test",
-            token_type="bearer",
+            token_type="Bearer",
             scope="read write",
         )
 
@@ -394,7 +398,7 @@ async def test_validate_token_scopes_subset(self, oauth_provider, client_metadat
         oauth_provider.client_metadata = client_metadata
         token = OAuthToken(
             access_token="test",
-            token_type="bearer",
+            token_type="Bearer",
             scope="read",
         )
 
@@ -409,7 +413,7 @@ async def test_validate_token_scopes_unauthorized(
         oauth_provider.client_metadata = client_metadata
         token = OAuthToken(
             access_token="test",
-            token_type="bearer",
+            token_type="Bearer",
             scope="read write admin",  # Includes unauthorized "admin"
         )
 
@@ -423,7 +427,7 @@ async def test_validate_token_scopes_no_requested(self, oauth_provider):
         oauth_provider.client_metadata.scope = None
         token = OAuthToken(
             access_token="test",
-            token_type="bearer",
+            token_type="Bearer",
             scope="admin super",
         )
 
@@ -530,7 +534,7 @@ async def test_refresh_access_token_success(
 
         new_token = OAuthToken(
             access_token="new_access_token",
-            token_type="bearer",
+            token_type="Bearer",
             expires_in=3600,
             refresh_token="new_refresh_token",
             scope="read write",
@@ -563,7 +567,7 @@ async def test_refresh_access_token_no_refresh_token(self, oauth_provider):
         """Test token refresh with no refresh token."""
         oauth_provider._current_tokens = OAuthToken(
             access_token="test",
-            token_type="bearer",
+            token_type="Bearer",
             # No refresh_token
         )
 
@@ -756,7 +760,8 @@ async def test_async_auth_flow_no_token(self, oauth_provider):
             # No Authorization header should be added if no token
             assert "Authorization" not in updated_request.headers
 
-    def test_scope_priority_client_metadata_first(
+    @pytest.mark.anyio
+    async def test_scope_priority_client_metadata_first(
         self, oauth_provider, oauth_client_info
     ):
         """Test that client metadata scope takes priority."""
@@ -785,7 +790,8 @@ def test_scope_priority_client_metadata_first(
 
         assert auth_params["scope"] == "read write"
 
-    def test_scope_priority_no_client_metadata_scope(
+    @pytest.mark.anyio
+    async def test_scope_priority_no_client_metadata_scope(
         self, oauth_provider, oauth_client_info
     ):
         """Test that no scope parameter is set when client metadata has no scope."""

tests/server/fastmcp/auth/test_auth_integration.py

@@ -96,7 +96,7 @@ async def exchange_authorization_code(
 
         return OAuthToken(
             access_token=access_token,
-            token_type="bearer",
+            token_type="Bearer",
             expires_in=3600,
             scope="read write",
             refresh_token=refresh_token,
@@ -160,7 +160,7 @@ async def exchange_refresh_token(
 
         return OAuthToken(
             access_token=new_access_token,
-            token_type="bearer",
+            token_type="Bearer",
             expires_in=3600,
             scope=" ".join(scopes) if scopes else " ".join(token_info.scopes),
             refresh_token=new_refresh_token,
@@ -831,7 +831,7 @@ async def test_authorization_get(
         assert "token_type" in token_response
         assert "refresh_token" in token_response
         assert "expires_in" in token_response
-        assert token_response["token_type"] == "bearer"
+        assert token_response["token_type"] == "Bearer"
 
         # 5. Verify the access token
         access_token = token_response["access_token"]