diff --git a/context.go b/context.go
new file mode 100644
index 0000000..04ef191
--- /dev/null
+++ b/context.go
@@ -0,0 +1,18 @@
+package tether
+
+import "gorm.io/gorm"
+
+type AuthCtx struct {
+	UserID     string
+	IsLoggedIn bool
+}
+
+type QueryCtx struct {
+	DB      *gorm.DB
+	AuthCtx *AuthCtx
+}
+
+type MutationCtx struct {
+	DB      *gorm.DB
+	AuthCtx *AuthCtx
+}
diff --git a/engine.go b/engine.go
index 4100c4b..f21853e 100644
--- a/engine.go
+++ b/engine.go
@@ -6,10 +6,16 @@ import (
 )
 
 type Engine struct {
-	db       *gorm.DB
-	channels map[string]*reactivity.Channel
+	db        *gorm.DB
+	channels  map[string]*reactivity.Channel
+	mutations []func(ctx *MutationCtx) error
+	queries   []func(ctx *QueryCtx) error
 }
 
 func NewEngine(db *gorm.DB) *Engine {
 	return &Engine{db: db, channels: make(map[string]*reactivity.Channel)}
 }
+
+func (e *Engine) RegisterMutation(mutation func(ctx *MutationCtx) error) {
+	e.mutations = append(e.mutations, mutation)
+}