MCP Server: Circular Reference when setting ToolCallbackProvider when ChatClient is used for Tools

[murphye]

Bug description

I have an example project with 3 separate MCP Servers, but I am focusing on the pets-service MCP Server example:
https://github.com/murphye/mcp-agentgateway-spring-ai-demo

To get Tools to list for an MCP Client, I have to add some extra code per the Spring MCP Server documentation, where PetsService contains my @Tools:

    @Bean
    fun petsTools(petsService: PetsService): ToolCallbackProvider {
        return MethodToolCallbackProvider.builder().toolObjects(petsService).build()
    }

When adding the ToolCallbackProvider code as specified, and if I have a ChatClient used for my @Tools, it create a circular dependency error for toolCallbackResolver.

@Service
class PetsService(private val chatClientBuilder: ChatClient.Builder) {
//...

    private val chatClient: ChatClient by lazy {
        chatClientBuilder.build()
    }
//...

    @Tool(description = "Search for available dogs for adoption")
    fun searchDogs(criteria: String): String {
//...
        
        val response = chatClient.prompt()
            .user("Based on the search criteria '$criteria', recommend dogs from this list:\n$dogsInfo")
            .call()
            .content()

        return response ?: "No dogs found matching your criteria."
    }

Error:

The dependencies of some of the beans in the application context form a cycle:

   petsApplication (field private com.demo.pets.PetsService com.demo.pets.PetsApplication.petsService)
┌─────┐
|  petsService defined in file [/Users/insite/Documents/GitHub/mcp-agentgateway-spring-ai-demo/pets-service/target/classes/com/demo/pets/PetsService.class]
↑     ↓
|  chatClientBuilder defined in class path resource [org/springframework/ai/model/chat/client/autoconfigure/ChatClientAutoConfiguration.class]
↑     ↓
|  anthropicChatModel defined in class path resource [org/springframework/ai/model/anthropic/autoconfigure/AnthropicChatAutoConfiguration.class]
↑     ↓
|  toolCallingManager defined in class path resource [org/springframework/ai/model/tool/autoconfigure/ToolCallingAutoConfiguration.class]
↑     ↓
|  toolCallbackResolver defined in class path resource [org/springframework/ai/model/tool/autoconfigure/ToolCallingAutoConfiguration.class]
↑     ↓
|  petsTools defined in class path resource [com/demo/pets/PetsMcpConfig.class]
└─────┘

Environment

I am currently using Spring AI 1.1.0-SNAPSHOT.

Steps to reproduce

1. Open PetsMcpConfig.kt.
2. Uncomment fun petsTools(petsService: PetsService): ToolCallbackProvider
3. mvn compile spring-boot:test -pl pets-service (Docker must be running)
4. Note that a circular reference error happens for toolCallbackResolver

Expected behavior

No circular references error if must configure ToolCallbackProvider

Minimal Complete Reproducible example

See steps to reproduce for the example.

[murphye]

I found a workaround using @Lazy to avoid the error, but this is not ideal:

@Configuration
class PetsMcpConfig(@Lazy val petsService: PetsService) {
//...

    @Bean
     fun petsTools(): ToolCallbackProvider {
        return MethodToolCallbackProvider.builder().toolObjects(petsService).build()
    }

[hbsjz-swl]

Hi, or you can create the searchDogs tool method into a separate Bean and add it to the MethodToolCallbackProvider as a tool provider Bean, which will improve the circular dependency problem of the Bean.