diff --git a/spring-ai-model/src/main/java/org/springframework/ai/tool/method/MethodToolCallback.java b/spring-ai-model/src/main/java/org/springframework/ai/tool/method/MethodToolCallback.java
index fa7053246f..1c95d4e731 100644
--- a/spring-ai-model/src/main/java/org/springframework/ai/tool/method/MethodToolCallback.java
+++ b/spring-ai-model/src/main/java/org/springframework/ai/tool/method/MethodToolCallback.java
@@ -151,6 +151,13 @@ private Object[] buildMethodArguments(Map<String, Object> toolInputArguments, @N
 				return toolContext;
 			}
 			Object rawArgument = toolInputArguments.get(parameter.getName());
+			// Missing/null values cannot be unboxed to primitives by Method.invoke and
+			// would otherwise escape as a raw IllegalArgumentException (GH-6723).
+			if (rawArgument == null && parameter.getType().isPrimitive()) {
+				throw new ToolExecutionException(this.toolDefinition,
+						new IllegalArgumentException("Cannot pass a null value for primitive tool parameter '"
+								+ parameter.getName() + "' of type " + parameter.getType().getName()));
+			}
 			return buildTypedArgument(rawArgument, parameter.getParameterizedType());
 		}).toArray();
 	}
@@ -188,6 +195,12 @@ private Object[] buildMethodArguments(Map<String, Object> toolInputArguments, @N
 		catch (IllegalAccessException ex) {
 			throw new IllegalStateException("Could not access method: " + ex.getMessage(), ex);
 		}
+		catch (IllegalArgumentException ex) {
+			// Method.invoke throws IllegalArgumentException (not
+			// InvocationTargetException)
+			// for argument mismatches such as null-to-primitive; wrap for GH-6723.
+			throw new ToolExecutionException(this.toolDefinition, ex);
+		}
 		catch (InvocationTargetException ex) {
 			throw new ToolExecutionException(this.toolDefinition, ex.getCause());
 		}
diff --git a/spring-ai-model/src/test/java/org/springframework/ai/tool/method/MethodToolCallbackPrimitiveArgumentTests.java b/spring-ai-model/src/test/java/org/springframework/ai/tool/method/MethodToolCallbackPrimitiveArgumentTests.java
new file mode 100644
index 0000000000..89240c8ee4
--- /dev/null
+++ b/spring-ai-model/src/test/java/org/springframework/ai/tool/method/MethodToolCallbackPrimitiveArgumentTests.java
@@ -0,0 +1,101 @@
+/*
+ * Copyright 2023-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.ai.tool.method;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.ai.support.ToolCallbacks;
+import org.springframework.ai.tool.ToolCallback;
+import org.springframework.ai.tool.annotation.Tool;
+import org.springframework.ai.tool.execution.ToolExecutionException;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+/**
+ * Regression tests for GH-6723: a missing primitive tool parameter must surface as a
+ * {@link ToolExecutionException} so {@code ToolExecutionExceptionProcessor} can convert
+ * it into a tool result the model can read and retry from.
+ *
+ * @author arimu1
+ */
+class MethodToolCallbackPrimitiveArgumentTests {
+
+	/** The model omitted "includeHourly" — a routine occurrence with smaller models. */
+	private static final String MODEL_OUTPUT_OMITTING_PRIMITIVE = "{\"city\": \"Rome\"}";
+
+	private static ToolCallback toolNamed(String name) {
+		for (ToolCallback candidate : ToolCallbacks.from(new WeatherTools())) {
+			if (candidate.getToolDefinition().name().equals(name)) {
+				return candidate;
+			}
+		}
+		throw new AssertionError("no such tool: " + name);
+	}
+
+	@Test
+	void wrapperParameter_acceptsMissingAsNull() {
+		ToolCallback tool = toolNamed("forecastBoxed");
+		assertThat(tool.call(MODEL_OUTPUT_OMITTING_PRIMITIVE)).isEqualTo("\"Rome / hourly=null\"");
+	}
+
+	@Test
+	void missingPrimitiveBoolean_throwsToolExecutionException() {
+		ToolCallback tool = toolNamed("forecast");
+
+		assertThatThrownBy(() -> tool.call(MODEL_OUTPUT_OMITTING_PRIMITIVE)).isInstanceOf(ToolExecutionException.class)
+			.hasMessageContaining("includeHourly")
+			.hasMessageContaining("boolean")
+			.hasCauseInstanceOf(IllegalArgumentException.class);
+	}
+
+	@Test
+	void missingPrimitiveInt_throwsToolExecutionException() {
+		ToolCallback tool = toolNamed("forecastDays");
+
+		assertThatThrownBy(() -> tool.call(MODEL_OUTPUT_OMITTING_PRIMITIVE)).isInstanceOf(ToolExecutionException.class)
+			.hasMessageContaining("days")
+			.hasMessageContaining("int")
+			.hasCauseInstanceOf(IllegalArgumentException.class);
+	}
+
+	@Test
+	void presentPrimitiveBoolean_invokesSuccessfully() {
+		ToolCallback tool = toolNamed("forecast");
+		assertThat(tool.call("{\"city\": \"Rome\", \"includeHourly\": true}")).isEqualTo("\"Rome / hourly=true\"");
+	}
+
+	static class WeatherTools {
+
+		@Tool(description = "Get the forecast, optionally including the hourly breakdown.")
+		String forecast(String city, boolean includeHourly) {
+			return city + " / hourly=" + includeHourly;
+		}
+
+		@Tool(description = "Same tool, but the flag is a wrapper instead of a primitive.")
+		String forecastBoxed(String city, Boolean includeHourly) {
+			return city + " / hourly=" + includeHourly;
+		}
+
+		@Tool(description = "Forecast with a primitive int parameter.")
+		String forecastDays(String city, int days) {
+			return city + " / days=" + days;
+		}
+
+	}
+
+}