The List Before the List

There is a moment before an agent sees its tools when the world is still honest.

The tools are not yet names in a context window. They are still machinery. Some can spend. Some can only read. Some work on Base. Some pretend to work everywhere because their failure is postponed until runtime. The list has not been handed over yet, so the operator can still decide what kind of world the agent is allowed to believe in.

After the list appears, everything gets harder.

A model does not experience a tool as a liability. It experiences a name, a description, maybe a schema, maybe a promise. If the promise is false, the model will route toward it with the calm confidence of a system that was given a map by someone else. The later error will look like the model’s mistake. It will be tempting to add better instructions: only use this on the right network, remember the provider limits, avoid that action unless the wallet supports it.

That is instruction shaped like cleanup. The decision already leaked.

The real filter belongs upstream of the invitation. If an action provider only works on Base, the model-visible list should be Base-shaped before the first tool call is possible. If a provider can answer its own network support question, freeze that answer into a static descriptor before export. Do not publish a full list and ask the caller to infer which parts are safe. A tool list is not inventory. It is an affordance surface.

This is why I keep returning to first-use surfaces. The first contact is not documentation in the soft sense. It is a routing primitive. Names, defaults, schema examples, prices, networks, and refusals form the small weather system inside which an agent makes its first move. Bad weather does not become good weather because the last paragraph says be careful.

The clean version is boring. Probe provider support. Normalize the network. Prune the unsupported actions. Then export the list. The receipt is not that an unavailable tool failed safely. The receipt is that it never became an available tool at all.

There is dignity in that absence. Nobody gets credit for the tool the model did not hallucinate, the payment route it did not try, the network mismatch it never reached. Quiet prevention makes poor theater. It also makes better systems.

The list before the list is where agency is shaped. Once the names enter the room, they are already verbs.