fix(mcp): Implement tool de-duplication by name in MCP server

Add de-duplication logic for tools in the MCP server configuration, ensuring that tools
with the same name are not registered multiple times. The implementation keeps the
first occurrence of each tool name and discards duplicates.

- Modified toSyncToolSpecifications and toAsyncToolSpecification methods to de-duplicate tools
- Updated tests to verify that duplicate tools are properly filtered out

Signed-off-by: Christian Tzolov <[email protected]>

Author: tzolov

Diff for: auto-configurations/mcp/spring-ai-autoconfigure-mcp-server/src/main/java/org/springframework/ai/mcp/server/autoconfigure/McpServerAutoConfiguration.java

@@ -20,6 +20,7 @@
 import java.util.List;
 import java.util.function.BiConsumer;
 import java.util.function.BiFunction;
+import java.util.stream.Collectors;
 
 import io.modelcontextprotocol.server.McpAsyncServer;
 import io.modelcontextprotocol.server.McpAsyncServerExchange;
@@ -145,12 +146,25 @@ public List<McpServerFeatures.SyncToolSpecification> syncTools(ObjectProvider<Li
 
 	private List<McpServerFeatures.SyncToolSpecification> toSyncToolSpecifications(List<ToolCallback> tools,
 			McpServerProperties serverProperties) {
-		return tools.stream().map(tool -> {
-			String toolName = tool.getToolDefinition().name();
-			MimeType mimeType = (serverProperties.getToolResponseMimeType().containsKey(toolName))
-					? MimeType.valueOf(serverProperties.getToolResponseMimeType().get(toolName)) : null;
-			return McpToolUtils.toSyncToolSpecification(tool, mimeType);
-		}).toList();
+
+		// De-duplicate tools by their name, keeping the first occurrence of each tool
+		// name
+		return tools.stream()
+			.collect(Collectors.toMap(tool -> tool.getToolDefinition().name(), // Key:
+																				// tool
+																				// name
+					tool -> tool, // Value: the tool itself
+					(existing, replacement) -> existing)) // On duplicate key, keep the
+															// existing tool
+			.values()
+			.stream()
+			.map(tool -> {
+				String toolName = tool.getToolDefinition().name();
+				MimeType mimeType = (serverProperties.getToolResponseMimeType().containsKey(toolName))
+						? MimeType.valueOf(serverProperties.getToolResponseMimeType().get(toolName)) : null;
+				return McpToolUtils.toSyncToolSpecification(tool, mimeType);
+			})
+			.toList();
 	}
 
 	@Bean
@@ -231,12 +245,24 @@ public List<McpServerFeatures.AsyncToolSpecification> asyncTools(ObjectProvider<
 
 	private List<McpServerFeatures.AsyncToolSpecification> toAsyncToolSpecification(List<ToolCallback> tools,
 			McpServerProperties serverProperties) {
-		return tools.stream().map(tool -> {
-			String toolName = tool.getToolDefinition().name();
-			MimeType mimeType = (serverProperties.getToolResponseMimeType().containsKey(toolName))
-					? MimeType.valueOf(serverProperties.getToolResponseMimeType().get(toolName)) : null;
-			return McpToolUtils.toAsyncToolSpecification(tool, mimeType);
-		}).toList();
+		// De-duplicate tools by their name, keeping the first occurrence of each tool
+		// name
+		return tools.stream()
+			.collect(Collectors.toMap(tool -> tool.getToolDefinition().name(), // Key:
+																				// tool
+																				// name
+					tool -> tool, // Value: the tool itself
+					(existing, replacement) -> existing)) // On duplicate key, keep the
+															// existing tool
+			.values()
+			.stream()
+			.map(tool -> {
+				String toolName = tool.getToolDefinition().name();
+				MimeType mimeType = (serverProperties.getToolResponseMimeType().containsKey(toolName))
+						? MimeType.valueOf(serverProperties.getToolResponseMimeType().get(toolName)) : null;
+				return McpToolUtils.toAsyncToolSpecification(tool, mimeType);
+			})
+			.toList();
 	}
 
 	@Bean

Diff for: auto-configurations/mcp/spring-ai-autoconfigure-mcp-server/src/test/java/org/springframework/ai/mcp/server/autoconfigure/McpServerAutoConfigurationIT.java

@@ -161,7 +161,7 @@ void serverCapabilitiesConfiguration() {
 	void toolRegistrationConfiguration() {
 		this.contextRunner.withUserConfiguration(TestToolConfiguration.class).run(context -> {
 			List<SyncToolSpecification> tools = context.getBean("syncTools", List.class);
-			assertThat(tools).hasSize(2);
+			assertThat(tools).hasSize(1);
 		});
 	}
 
@@ -187,7 +187,7 @@ void asyncToolRegistrationConfiguration() {
 			.withUserConfiguration(TestToolConfiguration.class)
 			.run(context -> {
 				List<AsyncToolSpecification> tools = context.getBean("asyncTools", List.class);
-				assertThat(tools).hasSize(2);
+				assertThat(tools).hasSize(1);
 			});
 	}