refactor: make CallToolRequest.Arguments more flexible (Breaking Change)

README.md

@@ -149,9 +149,21 @@ func main() {
 
     // Add the calculator handler
     s.AddTool(calculatorTool, func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
-        op := request.Params.Arguments["operation"].(string)
-        x := request.Params.Arguments["x"].(float64)
-        y := request.Params.Arguments["y"].(float64)
+        // Using helper functions for type-safe argument access
+        op, err := request.RequireString("operation")
+        if err != nil {
+            return mcp.NewToolResultError(err.Error()), nil
+        }
+
+        x, err := request.RequireFloat("x")
+        if err != nil {
+            return mcp.NewToolResultError(err.Error()), nil
+        }
+
+        y, err := request.RequireFloat("y")
+        if err != nil {
+            return mcp.NewToolResultError(err.Error()), nil
+        }
 
         var result float64
         switch op {
@@ -312,9 +324,10 @@ calculatorTool := mcp.NewTool("calculate",
 )
 
 s.AddTool(calculatorTool, func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
-    op := request.Params.Arguments["operation"].(string)
-    x := request.Params.Arguments["x"].(float64)
-    y := request.Params.Arguments["y"].(float64)
+    args := request.GetArguments()
+    op := args["operation"].(string)
+    x := args["x"].(float64)
+    y := args["y"].(float64)
 
     var result float64
     switch op {
@@ -355,10 +368,11 @@ httpTool := mcp.NewTool("http_request",
 )
 
 s.AddTool(httpTool, func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
-    method := request.Params.Arguments["method"].(string)
-    url := request.Params.Arguments["url"].(string)
+    args := request.GetArguments()
+    method := args["method"].(string)
+    url := args["url"].(string)
     body := ""
-    if b, ok := request.Params.Arguments["body"].(string); ok {
+    if b, ok := args["body"].(string); ok {
         body = b
     }
 

client/inprocess_test.go

@@ -32,7 +32,7 @@ func TestInProcessMCPClient(t *testing.T) {
 			Content: []mcp.Content{
 				mcp.TextContent{
 					Type: "text",
-					Text: "Input parameter: " + request.Params.Arguments["parameter-1"].(string),
+					Text: "Input parameter: " + request.GetArguments()["parameter-1"].(string),
 				},
 				mcp.AudioContent{
 					Type:     "audio",

client/sse_test.go

@@ -36,7 +36,7 @@ func TestSSEMCPClient(t *testing.T) {
 			Content: []mcp.Content{
 				mcp.TextContent{
 					Type: "text",
-					Text: "Input parameter: " + request.Params.Arguments["parameter-1"].(string),
+					Text: "Input parameter: " + request.GetArguments()["parameter-1"].(string),
 				},
 			},
 		}, nil

examples/custom_context/main.go

@@ -81,7 +81,7 @@ func handleMakeAuthenticatedRequestTool(
 	ctx context.Context,
 	request mcp.CallToolRequest,
 ) (*mcp.CallToolResult, error) {
-	message, ok := request.Params.Arguments["message"].(string)
+	message, ok := request.GetArguments()["message"].(string)
 	if !ok {
 		return nil, fmt.Errorf("missing message")
 	}

examples/dynamic_path/main.go

@@ -20,7 +20,7 @@ func main() {
 
 	// Add a trivial tool for demonstration
 	mcpServer.AddTool(mcp.NewTool("echo"), func(ctx context.Context, req mcp.CallToolRequest) (*mcp.CallToolResult, error) {
-		return mcp.NewToolResultText(fmt.Sprintf("Echo: %v", req.Params.Arguments["message"])), nil
+		return mcp.NewToolResultText(fmt.Sprintf("Echo: %v", req.GetArguments()["message"])), nil
 	})
 
 	// Use a dynamic base path based on a path parameter (Go 1.22+)

examples/everything/main.go

@@ -312,7 +312,7 @@ func handleEchoTool(
 	ctx context.Context,
 	request mcp.CallToolRequest,
 ) (*mcp.CallToolResult, error) {
-	arguments := request.Params.Arguments
+	arguments := request.GetArguments()
 	message, ok := arguments["message"].(string)
 	if !ok {
 		return nil, fmt.Errorf("invalid message argument")
@@ -331,7 +331,7 @@ func handleAddTool(
 	ctx context.Context,
 	request mcp.CallToolRequest,
 ) (*mcp.CallToolResult, error) {
-	arguments := request.Params.Arguments
+	arguments := request.GetArguments()
 	a, ok1 := arguments["a"].(float64)
 	b, ok2 := arguments["b"].(float64)
 	if !ok1 || !ok2 {
@@ -382,7 +382,7 @@ func handleLongRunningOperationTool(
 	ctx context.Context,
 	request mcp.CallToolRequest,
 ) (*mcp.CallToolResult, error) {
-	arguments := request.Params.Arguments
+	arguments := request.GetArguments()
 	progressToken := request.Params.Meta.ProgressToken
 	duration, _ := arguments["duration"].(float64)
 	steps, _ := arguments["steps"].(float64)