Passing your own context

Your tools need to know who is asking. Context is how that reaches them without going through the model.

Anything you like

A dataclass here, but it can be any object. The SDK never looks inside it.

@dataclass
class Customer:
    name: str
    plan: str

A tool that asks for it

Add a first parameter typed as RunContextWrapper and the SDK passes it in. The model never sees this parameter, so it does not appear in the tool's schema.

@function_tool
def my_plan(context: RunContextWrapper[Customer]) -> str:
    """Return the plan the current customer is on."""
    return f"{context.context.name} is on the {context.context.plan} plan."

context.context reads awkwardly the first time. The outer object is the SDK's wrapper, which also carries the usage so far; the inner one is yours.

result = await Runner.run(agent, "which plan am I on?", context=Customer("Asha", "annual"))
print(result.final_output)

The rule worth remembering

Context never reaches the model. It is your data, passed to your code. The model only learns about it if a tool returns some of it, which is exactly what happened here.

That makes it the right place for anything private: an account id, an internal customer record, a database handle, an API client. Nothing in there can leak into a prompt unless you put it there.