Support for the @PreAuthorize annotation in @Tool Components

[embesozzi]

Bug description
Currently, using this annotation does not work as expected and throws an exception. I believe this issue is related to the use of the @tool annotation.

The MCP Server is protected by OAuth 2.0 [1] and typically acts as an OAuth 2.0 resource server [2]. Therefore, we should be able to use scopes to protect the tool and handle OAuth-related errors appropriately, such as with the OAuth2AccessDeniedHandler.

[1] https://modelcontextprotocol.io/specification/2025-03-26
[2] https://docs.spring.io/spring-security/reference/servlet/oauth2/resource-server/jwt.html

Environment

<properties>
	<java.version>21</java.version>
	<spring-ai.version>1.0.0-M7</spring-ai.version>
</properties>

Steps to reproduce

1. Expose an API as an OAuth 2.0 Resource Server using spring.security.oauth2.resourceserver [2] or just follow this example https://spring.io/blog/2025/04/02/mcp-server-oauth2

2. Add the @PreAuthorize annotation to the Tool method:

@PreAuthorize("hasAuthority('SCOPE_read')")
@Tool(description = "Read users", name = "read_users")

Expected behavior
Using the @PreAuthorize annotation currently throws an error. I need to ensure that this triggers an appropriate OAuth2AccessDeniedHandler error.

[ThomasVitale]

@embesozzi thanks for reporting this issue. Is this still problem in version 1.0.0?

[embesozzi]

@ThomasVitale, thanks for the response. Yes, it's working in 1.0.0.
Just a quick question - is there a way to customize the OAuth2AccessDeniedHandler error in the case of MCP?
For instance, if I use something like @PreAuthorize("hasAuthority('SCOPE_READ_USERS')") in a controller, I'm able to customize the error message using @ControllerAdvice, for example:

@ControllerAdvice
public class OAuth2ExceptionHandler { ... }

Or in more complex scenarios with a CustomOAuth2AuthenticationEntryPoint or CustomOAuth2AccessDeniedHandler.

In the case of @tools in MCP we are in services (@service or @component), is there a way to intercept the error and customize the response?
Because customization is needed to ensure compliance with the OAuth 2.0 error message format in some cases.