diff --git a/pkg/llm-d-inference-sim/simulator.go b/pkg/llm-d-inference-sim/simulator.go
index 9656a5b..e3168a3 100644
--- a/pkg/llm-d-inference-sim/simulator.go
+++ b/pkg/llm-d-inference-sim/simulator.go
@@ -400,7 +400,7 @@ func (s *VllmSimulator) reqProcessingWorker(ctx context.Context, id int) {
 			if reqCtx.isChatCompletion && req.getToolChoice() != toolChoiceNone && req.getTools() != nil {
 				toolCalls, finishReason, completionTokens, err = createToolCalls(req.getTools(), req.getToolChoice())
 			}
-			if toolCalls == nil {
+			if toolCalls == nil && err == nil {
 				// Either no tool calls were defined, or we randomly chose not to create tool calls,
 				// so we generate a response text.
 				responseTokens, finishReason, completionTokens, err = req.createResponseText(s.mode)
diff --git a/pkg/llm-d-inference-sim/tools_test.go b/pkg/llm-d-inference-sim/tools_test.go
index 52ca9c1..a84f380 100644
--- a/pkg/llm-d-inference-sim/tools_test.go
+++ b/pkg/llm-d-inference-sim/tools_test.go
@@ -160,12 +160,16 @@ var toolWith3DArray = []openai.ChatCompletionToolParam{
 				"type": "object",
 				"properties": map[string]interface{}{
 					"tensor": map[string]interface{}{
-						"type": "array",
+						"type":     "array",
+						"minItems": 2,
 						"items": map[string]any{
-							"type": "array",
+							"type":     "array",
+							"minItems": 0,
+							"maxItems": 1,
 							"items": map[string]any{
-								"type":  "array",
-								"items": map[string]string{"type": "string"},
+								"type":     "array",
+								"items":    map[string]string{"type": "string"},
+								"maxItems": 3,
 							},
 						},
 						"description": "List of strings",
@@ -177,6 +181,28 @@ var toolWith3DArray = []openai.ChatCompletionToolParam{
 	},
 }
 
+var toolWithWrongMinMax = []openai.ChatCompletionToolParam{
+	{
+		Function: openai.FunctionDefinitionParam{
+			Name:        "multiply_numbers",
+			Description: openai.String("Multiply an array of numbers"),
+			Parameters: openai.FunctionParameters{
+				"type": "object",
+				"properties": map[string]interface{}{
+					"numbers": map[string]interface{}{
+						"type":        "array",
+						"items":       map[string]string{"type": "number"},
+						"description": "List of numbers to multiply",
+						"minItems":    3,
+						"maxItems":    1,
+					},
+				},
+				"required": []string{"numbers"},
+			},
+		},
+	},
+}
+
 var toolWithObjects = []openai.ChatCompletionToolParam{
 	{
 		Function: openai.FunctionDefinitionParam{
@@ -525,6 +551,14 @@ var _ = Describe("Simulator for request with tools", func() {
 			err = json.Unmarshal([]byte(tc.Function.Arguments), &args)
 			Expect(err).NotTo(HaveOccurred())
 			Expect(args["tensor"]).ToNot(BeEmpty())
+			tensor := args["tensor"]
+			Expect(len(tensor)).To(BeNumerically(">=", 2))
+			for _, elem := range tensor {
+				Expect(len(elem)).To(Or(Equal(0), Equal(1)))
+				for _, inner := range elem {
+					Expect(len(inner)).To(Or(Equal(1), Equal(2), Equal(3)))
+				}
+			}
 		},
 		func(mode string) string {
 			return "mode: " + mode
@@ -536,6 +570,32 @@ var _ = Describe("Simulator for request with tools", func() {
 		Entry(nil, modeRandom),
 	)
 
+	DescribeTable("array parameter with wrong min and max items, no streaming",
+		func(mode string) {
+			ctx := context.TODO()
+			client, err := startServer(ctx, mode)
+			Expect(err).NotTo(HaveOccurred())
+
+			openaiclient := openai.NewClient(
+				option.WithBaseURL(baseURL),
+				option.WithHTTPClient(client))
+
+			params := openai.ChatCompletionNewParams{
+				Messages:   []openai.ChatCompletionMessageParamUnion{openai.UserMessage(userMessage)},
+				Model:      model,
+				ToolChoice: openai.ChatCompletionToolChoiceOptionUnionParam{OfAuto: param.NewOpt("required")},
+				Tools:      toolWithWrongMinMax,
+			}
+
+			_, err = openaiclient.Chat.Completions.New(ctx, params)
+			Expect(err).To(HaveOccurred())
+		},
+		func(mode string) string {
+			return "mode: " + mode
+		},
+		Entry(nil, modeRandom),
+	)
+
 	DescribeTable("objects, no streaming",
 		func(mode string) {
 			ctx := context.TODO()
diff --git a/pkg/llm-d-inference-sim/tools_utils.go b/pkg/llm-d-inference-sim/tools_utils.go
index c6c3c5f..273dd08 100644
--- a/pkg/llm-d-inference-sim/tools_utils.go
+++ b/pkg/llm-d-inference-sim/tools_utils.go
@@ -53,7 +53,11 @@ func createToolCalls(tools []tool, toolChoice string) ([]toolCall, string, int,
 	// In case of 'required' at least one tool call has to be created, and we randomly choose
 	// the number of calls starting from one. Otherwise, we start from 0, and in case we randomly
 	// choose the number of calls to be 0, response text will be generated instead of a tool call.
-	numberOfCalls := randomInt(len(tools), toolChoice == toolChoiceRequired)
+	min := 0
+	if toolChoice == toolChoiceRequired {
+		min = 1
+	}
+	numberOfCalls := randomInt(min, len(tools))
 	if numberOfCalls == 0 {
 		return nil, "", 0, nil
 	}
@@ -61,7 +65,7 @@ func createToolCalls(tools []tool, toolChoice string) ([]toolCall, string, int,
 	calls := make([]toolCall, 0)
 	for i := range numberOfCalls {
 		// Randomly choose which tools to call. We may call the same tool more than once.
-		index := randomInt(len(tools)-1, false)
+		index := randomInt(0, len(tools)-1)
 		args, err := generateToolArguments(tools[index])
 		if err != nil {
 			return nil, "", 0, err
@@ -130,7 +134,7 @@ func createArgument(property any) (any, error) {
 	if ok {
 		enumArray, ok := enum.([]any)
 		if ok && len(enumArray) > 0 {
-			index := randomInt(len(enumArray)-1, false)
+			index := randomInt(0, len(enumArray)-1)
 			return enumArray[index], nil
 		}
 	}
@@ -139,13 +143,24 @@ func createArgument(property any) (any, error) {
 	case "string":
 		return getStringArgument(), nil
 	case "number":
-		return randomInt(100, false), nil
+		return randomInt(0, 100), nil
 	case "boolean":
 		return flipCoin(), nil
 	case "array":
 		items := propertyMap["items"]
 		itemsMap := items.(map[string]any)
-		numberOfElements := randomInt(5, true)
+		minItems := 1
+		maxItems := 5
+		if value, ok := propertyMap["minItems"]; ok {
+			minItems = int(value.(float64))
+		}
+		if value, ok := propertyMap["maxItems"]; ok {
+			maxItems = int(value.(float64))
+		}
+		if minItems > maxItems {
+			return nil, fmt.Errorf("minItems (%d) is greater than maxItems(%d)", minItems, maxItems)
+		}
+		numberOfElements := randomInt(minItems, maxItems)
 		array := make([]any, numberOfElements)
 		for i := range numberOfElements {
 			elem, err := createArgument(itemsMap)
@@ -177,7 +192,7 @@ func createArgument(property any) (any, error) {
 }
 
 func getStringArgument() string {
-	index := randomInt(len(fakeStringArguments)-1, false)
+	index := randomInt(0, len(fakeStringArguments)-1)
 	return fakeStringArguments[index]
 }
 
@@ -336,6 +351,14 @@ const schema = `{
           "items": {
             "type": "string"
           }
+        },
+          "minItems": {
+          "type": "integer",
+          "minimum": 0
+        },
+        "maxItems": {
+          "type": "integer",
+          "minimum": 0
         }
       },
       "required": [
diff --git a/pkg/llm-d-inference-sim/utils.go b/pkg/llm-d-inference-sim/utils.go
index e76e0d2..9701b04 100644
--- a/pkg/llm-d-inference-sim/utils.go
+++ b/pkg/llm-d-inference-sim/utils.go
@@ -62,7 +62,7 @@ func getMaxTokens(maxCompletionTokens *int64, maxTokens *int64) (*int64, error)
 // getRandomResponseText returns random response text from the pre-defined list of responses
 // considering max completion tokens if it is not nil, and a finish reason (stop or length)
 func getRandomResponseText(maxCompletionTokens *int64) (string, string) {
-	index := randomInt(len(chatCompletionFakeResponses)-1, false)
+	index := randomInt(0, len(chatCompletionFakeResponses)-1)
 	text := chatCompletionFakeResponses[index]
 
 	return getResponseText(maxCompletionTokens, text)
@@ -105,26 +105,22 @@ func randomNumericString(length int) string {
 	digits := "0123456789"
 	result := make([]byte, length)
 	for i := 0; i < length; i++ {
-		num := randomInt(9, false)
+		num := randomInt(0, 9)
 		result[i] = digits[num]
 	}
 	return string(result)
 }
 
-// Returns an integer between 0 and max (included), unless startFromeOne is true,
-// in which case returns an integer between 1 and max (included)
-func randomInt(max int, startFromOne bool) int {
+// Returns an integer between min and max (included)
+func randomInt(min int, max int) int {
 	src := rand.NewSource(time.Now().UnixNano())
 	r := rand.New(src)
-	if startFromOne {
-		return r.Intn(max) + 1 // [1, max]
-	}
-	return r.Intn(max + 1) // [0, max]
+	return r.Intn(max-min+1) + min
 }
 
 // Returns true or false randomly
 func flipCoin() bool {
-	return randomInt(1, false) != 0
+	return randomInt(0, 1) != 0
 }
 
 // Regular expression for the response tokenization