guard against nil tool definitions when building flagsets

Author: burmudar

internal/mcp/mcp_args.go

@@ -1,6 +1,7 @@
 package mcp
 
 import (
+	"errors"
 	"flag"
 	"fmt"
 	"reflect"
@@ -36,6 +37,9 @@ func DerefFlagValues(vars map[string]any) {
 }
 
 func BuildArgFlagSet(tool *ToolDef) (*flag.FlagSet, map[string]any, error) {
+	if tool == nil {
+		return nil, nil, errors.New("cannot build flagset on nil Tool Definition")
+	}
 	fs := flag.NewFlagSet(tool.Name, flag.ContinueOnError)
 	flagVars := map[string]any{}
 

internal/mcp/mcp_args_test.go

@@ -49,7 +49,7 @@ func TestFlagSetParse(t *testing.T) {
 		t.Fatalf("failed to load tool json: %v", err)
 	}
 
-	flagSet, vars, err := BuildArgFlagSet(defs["sg_test_tool"])
+	flagSet, vars, err := BuildArgFlagSet(defs["test-tool"])
 	if err != nil {
 		t.Fatalf("failed to build flagset from mcp tool definition: %v", err)
 	}