No tool methods found in the provided tool objects: +…

Error message

No tool methods found in the provided tool objects: + this.toolObjects

What it means

This is a warning (not an exception) logged by SyncMcpToolProvider.getToolSpecifications when reflection over the supplied @McpTool-annotated tool objects yields zero tool specifications. The provider still returns an empty list, so downstream MCP clients will see a server/tool provider with no tools. It indicates the tool objects were provided but none of their methods matched the tool annotation scan.

Solutions

Verify each object passed to the provider has at least one method annotated with @McpTool
Check that methods are public (or otherwise visible to the annotation scanner) and the mcp-annotations dependency is on the classpath
Log/inspect this.toolObjects at construction time to confirm the right beans are wired
Upgrade/align the spring-ai mcp-annotations version so the annotation the scanner looks for matches the one used in your code

Example fix

// before
SyncMcpToolProvider provider = SyncMcpToolProvider.builder()
    .toolObjects(new MyService()) // MyService has no @McpTool methods
    .build();
// after
public class MyService {
    @McpTool(name = "getWeather", description = "Get weather")
    public String getWeather(String city) { ... }
}
SyncMcpToolProvider provider = SyncMcpToolProvider.builder()
    .toolObjects(new MyService())
    .build();

Defensive patterns

Strategy: validation

Validate before calling

// before building the provider
long toolCount = java.util.Arrays.stream(toolObjects)
    .flatMap(o -> Arrays.stream(o.getClass().getDeclaredMethods()))
    .filter(m -> m.isAnnotationPresent(org.springframework.ai.mcp.annotation.McpTool.class))
    .count();
if (toolCount == 0) throw new IllegalStateException("No @McpTool methods found in tool objects");

Prevention

Always annotate at least one public method with @McpTool in each tool object
Write a startup assertion/test that the provider's getToolSpecifications() returns a non-empty list
Import @McpTool from the correct package
Check logs for this warning in integration tests before deploying

When it happens

Trigger: Calling SyncMcpToolProvider with tool objects whose classes have no @McpTool-annotated methods; annotation metadata not on the classpath so scanning finds nothing; passing the wrong (unrelated) objects as toolObjects; methods annotated with a custom/incorrect annotation name instead of @McpTool.

Common situations: Renaming or removing @McpTool annotations during refactoring; building tools with a non-public method visibility the scanner skips; wiring an empty or wrong bean list into the provider constructor; mixing mcp-annotations versions where the annotation package changed.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

AI-assisted analysis of spring-projects/spring-ai@98a7beda4f (2026-09-11). Data as JSON: /api/errors/2ac24593c165bc55. Report an issue: GitHub.

Appendix: source

Thrown at mcp/mcp-annotations/src/main/java/org/springframework/ai/mcp/annotation/provider/tool/SyncMcpToolProvider.java:154

					ReturnMode returnMode = useStructuredOtput ? ReturnMode.STRUCTURED
							: (methodReturnType == Void.TYPE || methodReturnType == void.class ? ReturnMode.VOID
									: ReturnMode.TEXT);

					BiFunction<McpSyncServerExchange, CallToolRequest, CallToolResult> methodCallback = new SyncMcpToolMethodCallback(
							returnMode, mcpToolMethod, toolObject);

					var toolSpec = SyncToolSpecification.builder().tool(tool).callHandler(methodCallback).build();

					return toolSpec;
				})
				.toList())
			.flatMap(List::stream)
			.toList();

		if (toolSpecs.isEmpty()) {
			if (logger.isWarnEnabled()) {
				logger.warn("No tool methods found in the provided tool objects: " + this.toolObjects);
			}
		}

		return toolSpecs;
	}

}

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