samples: client, improve comments on configuration files

Signed-off-by: Daniel Garnier-Moiroux <[email protected]>

Author: Kehrlann

samples/sample-mcp-client/src/main/java/org/springaicommunity/mcp/security/sample/client/McpConfiguration.java

@@ -23,6 +23,8 @@
 import org.springaicommunity.mcp.security.client.sync.oauth2.http.client.OAuth2AuthorizationCodeSyncHttpRequestCustomizer;
 
 import org.springframework.ai.mcp.customizer.McpSyncClientCustomizer;
+import org.springframework.ai.model.anthropic.autoconfigure.AnthropicChatAutoConfiguration;
+import org.springframework.ai.model.tool.autoconfigure.ToolCallingAutoConfiguration;
 import org.springframework.ai.tool.resolution.StaticToolCallbackResolver;
 import org.springframework.ai.tool.resolution.ToolCallbackResolver;
 import org.springframework.context.annotation.Bean;
@@ -34,6 +36,26 @@
 @Configuration
 class McpConfiguration {
 
+	/**
+	 * If the default {@link ToolCallbackResolver} from
+	 * {@link ToolCallingAutoConfiguration} is imported, then all MCP-based tools are
+	 * added to the resolver. In order to do so, the {@link ToolCallbackResolver} bean
+	 * lists all MCP tools, therefore initializing MCP clients and listing the tools.
+	 * <p>
+	 * This is an issue when the MCP server is secured with OAuth2, because to obtain a
+	 * token, a user must be involved in the flow, and there is no user present on app
+	 * startup.
+	 * <p>
+	 * To avoid this issue, we must exclude the default {@link ToolCallbackResolver}. We
+	 * can't easily disable the entire {@link ToolCallingAutoConfiguration} class, because
+	 * it is imported directly by the chat model configurations, such as
+	 * {@link AnthropicChatAutoConfiguration}. Instead, we provide a default, no-op bean.
+	 */
+	@Bean
+	ToolCallbackResolver resolver() {
+		return new StaticToolCallbackResolver(List.of());
+	}
+
 	@Bean
 	McpSyncHttpClientRequestCustomizer requestCustomizer(OAuth2AuthorizedClientManager oAuth2AuthorizedClientManager,
 			ClientRegistrationRepository clientRegistrationRepository) {
@@ -46,6 +68,10 @@ McpSyncClientCustomizer syncClientCustomizer() {
 		return (name, syncSpec) -> syncSpec.transportContextProvider(new AuthenticationMcpTransportContextProvider());
 	}
 
+	/**
+	 * Returns the ID of the {@code spring.security.oauth2.client.registration}, if
+	 * unique.
+	 */
 	private static String findUniqueClientRegistration(ClientRegistrationRepository clientRegistrationRepository) {
 		String registrationId;
 		if (!(clientRegistrationRepository instanceof InMemoryClientRegistrationRepository repo)) {