diff --git a/src/interface.jl b/src/interface.jl
index f873e4f..54a1ff7 100644
--- a/src/interface.jl
+++ b/src/interface.jl
@@ -51,13 +51,13 @@ julia>
 
 # TODO
   [] update docstring
-  [PENDING] implement the function
+  [x] implement the function
   [] implement RAG to pull similar experience
   [] use iterative prompting to ensure JSON format
 
 # Signature
 """
-function decisionMaker(a::T1, state::T2) where {T1<:agent, T2<:AbstractDict}
+function decisionMaker(a::T1, state::T2)::String where {T1<:agent, T2<:AbstractDict}
   customerinfo = 
   """
   I will give you the following information about customer: