> ## Documentation Index
> Fetch the complete documentation index at: https://docs.getmillwork.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Models, agents, and skills

> Learn how Solver works with registered models, agent endpoints, and skills.

Solver needs a clear set of options before it can choose. The API calls each
registered option an **arm**. In plain English, an arm is one way Solver can do
the work.

<CardGroup cols={3}>
  <Card title="Model" icon="brain-circuit">
    A tested model route saved from your organization's live catalog.
  </Card>

  <Card title="Agent endpoint" icon="bot">
    An HTTPS endpoint your organization operates and registers with Millwork.
  </Card>

  <Card title="Skill" icon="file-code-2">
    A versioned, hashed procedure that can take part in bounded, reviewed repair.
  </Card>
</CardGroup>

## Registration is permission to consider

Registration makes an arm available for eligibility checks. Selection happens
separately for each run.

For a current public run, Solver keeps arms that are ready and permitted for
every declared data class. It deterministically ranks that eligible set using
the configured cost preference.

## Why registration matters

Registration moves route selection out of scattered application logic. Each
option gets a stable identity, readiness state, data grants, and evidence trail.
The task can stay focused on the outcome instead of carrying a provider secret
or endpoint decision.

## Start with a model

The current private-preview quickstart begins with a model arm. Choose a model
from your organization's live catalog and submit the registration template
exactly as the catalog returns it.

Agent arms belong to your organization and call the HTTPS endpoint it registers.
Skill arms are an advanced path. Any repair proposal requires explicit approval
before it changes the saved skill.

<Card title="Run your first model" icon="play" href="/get-started/builder">
  Add one catalog model and follow a live run to its receipt.
</Card>