Documentation says:
// Create agent with a single context prompt and two tools
while I see only one tool - Adder:
// Create agent with a single context prompt and two tools
let calculator_agent = openai_client
.agent(providers::openai::GPT_4O)
.preamble("You are a calculator here to help the user perform arithmetic operations. Use the tools provided to answer the user's question.")
.max_tokens(1024)
.tool(Adder)
.build();