diff --git a/internal/swmcp/server.go b/internal/swmcp/server.go
index e5307d4..c24e888 100644
--- a/internal/swmcp/server.go
+++ b/internal/swmcp/server.go
@@ -93,11 +93,25 @@ func WithSkyWalkingAuth(ctx context.Context, username, password string) context.
 // The value is sourced from the CLI/config binding for `--sw-url`,
 // falling back to the built-in default when unset.
 func configuredSkyWalkingURL() string {
+	resolvedURL, err := resolvedConfiguredSkyWalkingURL()
+	if err != nil {
+		logrus.WithError(err).Warn("invalid SkyWalking OAP URL configuration; falling back to default URL")
+		return config.DefaultSWURL
+	}
+	return resolvedURL
+}
+
+func resolvedConfiguredSkyWalkingURL() (string, error) {
 	urlStr := viper.GetString("url")
 	if urlStr == "" {
 		urlStr = config.DefaultSWURL
 	}
-	return tools.FinalizeURL(urlStr)
+	return tools.NormalizeOAPURL(urlStr)
+}
+
+func validateConfiguredSkyWalkingURL() error {
+	_, err := resolvedConfiguredSkyWalkingURL()
+	return err
 }
 
 // resolveEnvVar resolves a value that may contain an environment variable reference
diff --git a/internal/swmcp/server_test.go b/internal/swmcp/server_test.go
index 1007e56..8ec433e 100644
--- a/internal/swmcp/server_test.go
+++ b/internal/swmcp/server_test.go
@@ -22,6 +22,7 @@ import (
 	"testing"
 
 	"github.com/apache/skywalking-cli/pkg/contextkey"
+	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
 
 	"github.com/apache/skywalking-mcp/internal/config"
@@ -52,6 +53,43 @@ func TestConfiguredSkyWalkingURLFinalizesConfiguredValue(t *testing.T) {
 	}
 }
 
+func TestConfiguredSkyWalkingURLFallsBackToDefaultOnInvalidValue(t *testing.T) {
+	t.Cleanup(viper.Reset)
+	viper.Set("url", "ftp://configured-oap.example.com:12800")
+
+	got := configuredSkyWalkingURL()
+	if got != config.DefaultSWURL {
+		t.Fatalf("configuredSkyWalkingURL() = %q, want %q", got, config.DefaultSWURL)
+	}
+}
+
+func TestValidateConfiguredSkyWalkingURLRejectsUnsupportedScheme(t *testing.T) {
+	t.Cleanup(viper.Reset)
+	viper.Set("url", "ftp://configured-oap.example.com:12800")
+
+	err := validateConfiguredSkyWalkingURL()
+	if err == nil {
+		t.Fatal("validateConfiguredSkyWalkingURL() error = nil, want error")
+	}
+}
+
+func TestTransportCommandsRejectInvalidSWURL(t *testing.T) {
+	t.Cleanup(viper.Reset)
+	viper.Set("url", "ftp://configured-oap.example.com:12800")
+
+	for name, cmd := range map[string]*cobra.Command{
+		"stdio":      NewStdioServer(),
+		"sse":        NewSSEServer(),
+		"streamable": NewStreamable(),
+	} {
+		t.Run(name, func(t *testing.T) {
+			if err := cmd.RunE(cmd, nil); err == nil {
+				t.Fatal("RunE() error = nil, want invalid sw-url error")
+			}
+		})
+	}
+}
+
 func TestResolveEnvVar(t *testing.T) {
 	t.Setenv("SW_TEST_SECRET", "resolved-secret")
 
diff --git a/internal/swmcp/sse.go b/internal/swmcp/sse.go
index ae06a07..0dab635 100644
--- a/internal/swmcp/sse.go
+++ b/internal/swmcp/sse.go
@@ -41,6 +41,10 @@ func NewSSEServer() *cobra.Command {
 		Short: "Start SSE server",
 		Long:  `Start a server that listens for Server-Sent Events (SSE) on the specified address.`,
 		RunE: func(_ *cobra.Command, _ []string) error {
+			if err := validateConfiguredSkyWalkingURL(); err != nil {
+				return err
+			}
+
 			sseServerConfig := config.SSEServerConfig{
 				Address:  viper.GetString("sse-address"),
 				BasePath: viper.GetString("base-path"),
diff --git a/internal/swmcp/stdio.go b/internal/swmcp/stdio.go
index 02abb4a..12fe05b 100644
--- a/internal/swmcp/stdio.go
+++ b/internal/swmcp/stdio.go
@@ -41,6 +41,10 @@ func NewStdioServer() *cobra.Command {
 		Short: "Start stdio server",
 		Long:  `Start a server that communicates via standard input/output streams using JSON-RPC messages.`,
 		RunE: func(_ *cobra.Command, _ []string) error {
+			if err := validateConfiguredSkyWalkingURL(); err != nil {
+				return err
+			}
+
 			stdioServerConfig := config.StdioServerConfig{
 				URL:         viper.GetString("url"),
 				ReadOnly:    viper.GetBool("read-only"),
diff --git a/internal/swmcp/streamable.go b/internal/swmcp/streamable.go
index 0f85fb1..5d692ad 100644
--- a/internal/swmcp/streamable.go
+++ b/internal/swmcp/streamable.go
@@ -36,6 +36,10 @@ func NewStreamable() *cobra.Command {
 		Short: "Start Streamable server",
 		Long:  `Starting SkyWalking MCP server with Streamable HTTP transport.`,
 		RunE: func(_ *cobra.Command, _ []string) error {
+			if err := validateConfiguredSkyWalkingURL(); err != nil {
+				return err
+			}
+
 			streamableConfig := config.StreamableServerConfig{
 				Address:      viper.GetString("address"),
 				EndpointPath: viper.GetString("endpoint-path"),
diff --git a/internal/tools/common.go b/internal/tools/common.go
index 86b8fcb..83e3db2 100644
--- a/internal/tools/common.go
+++ b/internal/tools/common.go
@@ -45,18 +45,37 @@ const (
 
 // FinalizeURL ensures the URL ends with "/graphql".
 func FinalizeURL(urlStr string) string {
-	if !strings.HasSuffix(urlStr, "/graphql") {
-		urlStr = strings.TrimRight(urlStr, "/") + "/graphql"
+	normalizedURL, err := NormalizeOAPURL(urlStr)
+	if err == nil {
+		return normalizedURL
 	}
 	return urlStr
 }
 
-// validateURLScheme ensures the URL uses http or https.
-func validateURLScheme(rawURL string) error {
+// NormalizeOAPURL parses and validates the OAP URL, then ensures the path ends with /graphql.
+func NormalizeOAPURL(rawURL string) (string, error) {
 	u, err := url.Parse(rawURL)
 	if err != nil {
-		return fmt.Errorf("invalid OAP URL: %w", err)
+		return "", fmt.Errorf("invalid OAP URL: %w", err)
+	}
+	if err := validateURLScheme(u); err != nil {
+		return "", err
+	}
+	if u.Host == "" {
+		return "", fmt.Errorf("invalid OAP URL %q: host is required", rawURL)
+	}
+
+	if u.Path == "" || u.Path == "/" {
+		u.Path = "/graphql"
+	} else if !strings.HasSuffix(u.Path, "/graphql") {
+		u.Path = strings.TrimRight(u.Path, "/") + "/graphql"
 	}
+
+	return u.String(), nil
+}
+
+// validateURLScheme ensures the URL uses http or https.
+func validateURLScheme(u *url.URL) error {
 	if u.Scheme != "http" && u.Scheme != "https" {
 		return fmt.Errorf("unsupported OAP URL scheme %q: only http and https are allowed", u.Scheme)
 	}
diff --git a/internal/tools/common_test.go b/internal/tools/common_test.go
index eb60ce1..29e06b7 100644
--- a/internal/tools/common_test.go
+++ b/internal/tools/common_test.go
@@ -17,6 +17,7 @@
 package tools
 
 import (
+	"strings"
 	"testing"
 	"time"
 
@@ -39,6 +40,7 @@ func TestFinalizeURL(t *testing.T) {
 		{name: "adds graphql suffix", in: "http://localhost:12800", want: "http://localhost:12800/graphql"},
 		{name: "trims trailing slash", in: "http://localhost:12800/", want: "http://localhost:12800/graphql"},
 		{name: "keeps existing graphql", in: "http://localhost:12800/graphql", want: "http://localhost:12800/graphql"},
+		{name: "preserves query string", in: "http://localhost:12800?x=1", want: "http://localhost:12800/graphql?x=1"},
 	}
 
 	for _, tc := range tests {
@@ -50,6 +52,44 @@ func TestFinalizeURL(t *testing.T) {
 	}
 }
 
+func TestNormalizeOAPURL(t *testing.T) {
+	tests := []struct {
+		name    string
+		in      string
+		want    string
+		wantErr string
+	}{
+		{name: "http", in: "http://localhost:12800", want: "http://localhost:12800/graphql"},
+		{name: "https", in: "https://localhost:12800/graphql", want: "https://localhost:12800/graphql"},
+		{name: "preserves query and fragment", in: "https://localhost:12800/oap?debug=1#frag", want: "https://localhost:12800/oap/graphql?debug=1#frag"},
+		{name: "rejects unsupported scheme", in: "ftp://localhost:12800", wantErr: "unsupported OAP URL scheme \"ftp\""},
+		{name: "rejects missing host", in: "http://", wantErr: "host is required"},
+		{name: "rejects malformed hostless path", in: "http:/foo", wantErr: "host is required"},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			got, err := NormalizeOAPURL(tc.in)
+			if tc.wantErr != "" {
+				if err == nil {
+					t.Fatalf("NormalizeOAPURL(%q) error = nil, want %q", tc.in, tc.wantErr)
+				}
+				if !strings.Contains(err.Error(), tc.wantErr) {
+					t.Fatalf("NormalizeOAPURL(%q) error = %q, want substring %q", tc.in, err.Error(), tc.wantErr)
+				}
+				return
+			}
+
+			if err != nil {
+				t.Fatalf("NormalizeOAPURL(%q) unexpected error: %v", tc.in, err)
+			}
+			if got != tc.want {
+				t.Fatalf("NormalizeOAPURL(%q) = %q, want %q", tc.in, got, tc.want)
+			}
+		})
+	}
+}
+
 func TestParseTimezoneOffset(t *testing.T) {
 	loc, ok := parseTimezoneOffset("+0830")
 	if !ok {
diff --git a/internal/tools/mqe.go b/internal/tools/mqe.go
index e9f4e5c..032d456 100644
--- a/internal/tools/mqe.go
+++ b/internal/tools/mqe.go
@@ -91,9 +91,8 @@ func getContextBool(ctx context.Context, key any) bool {
 // executeGraphQLWithContext executes a GraphQL query using URL and auth from context.
 func executeGraphQLWithContext(ctx context.Context, query string, variables map[string]interface{}) (*GraphQLResponse, error) {
 	rawURL := getContextString(ctx, contextkey.BaseURL{})
-	rawURL = FinalizeURL(rawURL)
-
-	if err := validateURLScheme(rawURL); err != nil {
+	normalizedURL, err := NormalizeOAPURL(rawURL)
+	if err != nil {
 		return nil, err
 	}
 
@@ -107,7 +106,7 @@ func executeGraphQLWithContext(ctx context.Context, query string, variables map[
 		return nil, fmt.Errorf("failed to marshal GraphQL request: %w", err)
 	}
 
-	req, err := http.NewRequestWithContext(ctx, "POST", rawURL, bytes.NewBuffer(jsonData))
+	req, err := http.NewRequestWithContext(ctx, "POST", normalizedURL, bytes.NewBuffer(jsonData))
 	if err != nil {
 		return nil, fmt.Errorf("failed to create HTTP request: %w", err)
 	}