spring-projects/spring-ai · error · IllegalArgumentException

First parameter must be of type LoggingLevel:

Error message

First parameter must be of type LoggingLevel: 

What it means

Parameter validation in AbstractMcpLoggingMethodCallback.validateParameters for a 3-parameter logging handler: parameters[0] is not a LoggingLevel, so the (LoggingLevel, String, String) signature convention is violated.

Source

Thrown at mcp/mcp-annotations/src/main/java/org/springframework/ai/mcp/annotation/method/logging/AbstractMcpLoggingMethodCallback.java:113

			throw new IllegalArgumentException(
					"Method must have either 1 parameter (LoggingMessageNotification) or 3 parameters (LoggingLevel, String, String): "
							+ method.getName() + " in " + method.getDeclaringClass().getName() + " has "
							+ parameters.length + " parameters");
		}

		// Check parameter types
		if (parameters.length == 1) {
			// Single parameter must be LoggingMessageNotification
			if (!LoggingMessageNotification.class.isAssignableFrom(parameters[0].getType())) {
				throw new IllegalArgumentException("Single parameter must be of type LoggingMessageNotification: "
						+ method.getName() + " in " + method.getDeclaringClass().getName() + " has parameter of type "
						+ parameters[0].getType().getName());
			}
		}
		else {
			// Three parameters must be LoggingLevel, String, String
			if (!LoggingLevel.class.isAssignableFrom(parameters[0].getType())) {
				throw new IllegalArgumentException("First parameter must be of type LoggingLevel: " + method.getName()
						+ " in " + method.getDeclaringClass().getName() + " has parameter of type "
						+ parameters[0].getType().getName());
			}
			if (!String.class.isAssignableFrom(parameters[1].getType())) {
				throw new IllegalArgumentException("Second parameter must be of type String: " + method.getName()
						+ " in " + method.getDeclaringClass().getName() + " has parameter of type "
						+ parameters[1].getType().getName());
			}
			if (!String.class.isAssignableFrom(parameters[2].getType())) {
				throw new IllegalArgumentException("Third parameter must be of type String: " + method.getName()
						+ " in " + method.getDeclaringClass().getName() + " has parameter of type "
						+ parameters[2].getType().getName());
			}
		}
	}

	/**
	 * Builds the arguments array for invoking the method.

View on GitHub (pinned to 98a7beda4f)

Solutions

1. Change the first parameter to LoggingLevel
2. Or use the single-parameter form taking LoggingMessageNotification

Example fix

// before
@McpLogging(clients = "client1")
public void onLog(java.util.logging.Level level, String logger, String msg) { ... }
// after
@McpLogging(clients = "client1")
public void onLog(LoggingLevel level, String logger, String msg) { ... }

if (m.getParameterCount() == 3
        && !LoggingLevel.class.isAssignableFrom(m.getParameterTypes()[0])) {
    throw new IllegalStateException("first param must be LoggingLevel");
}

static boolean firstParamIsLoggingLevel(Method m) {
    return m.getParameterCount() == 3
        && LoggingLevel.class.isAssignableFrom(m.getParameterTypes()[0]);
}

When it happens

Trigger: Registering a @McpLogging method with signature (String, String, String) or (Level, String, String) instead of (LoggingLevel, String, String).

Common situations: Developer uses java.util.logging.Level or a custom severity enum instead of the MCP SDK's LoggingLevel; parameter order confused with (message, level, logger) conventions from other logging frameworks.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

• Single parameter must be of type LoggingMessageNotification:
• Second parameter must be of type String:
• Third parameter must be of type String:
• Parameter must be of type List<McpSchema.Resource>:
• Method must not be null

AI-assisted analysis of spring-projects/spring-ai@98a7beda4f (2026-09-11). Data as JSON: /api/errors/8af9855854843907. Report an issue: GitHub.