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

# Data accessors

> Exposing your data to flows through the module namespace.

A data accessor lets a flow read your module's data without ever copying it into
session state. The flow asks for `module.hr.department`; the engine resolves it
through the accessor registered under the namespace `hr`.

## The contract

```php theme={"theme":"one-dark-pro"}
interface DataAccessorInterface
{
    /** Namespace of this accessor, e.g. "hr". Maps to module.{namespace}.* */
    public function namespace(): string;

    /** @return mixed scalar or null; must not return objects */
    public function get(string $key, string $contactId, string $tenantId): mixed;

    /** @return string[] Supported keys, used to validate a flow on save */
    public function supportedKeys(): array;
}
```

Register it from your service provider:

```php theme={"theme":"one-dark-pro"}
protected function registerExtensions(CoreRegistrarInterface $registrar): void
{
    $registrar->registerDataAccessor('hr', HrDataAccessor::class);
}
```

## Why this exists

<Warning>
  A condition node must never read module tables directly.
</Warning>

If HR data were read straight from its tables by the flow engine, the engine would
have to know the module's schema — and every schema change would become a flow
engine change. If it were copied into session state instead, every running session
would carry a snapshot that was correct when the session started and wrong an hour
later.

Resolving through an accessor avoids both. The module stays the single source of
truth, the engine stays ignorant of its tables, and the flow always sees current
data.

## Implementation notes

**Return scalars or null.** The accessor sits on a boundary that has to serialise;
returning an object pushes your internal shape into the engine.

**`supportedKeys()` is validation, not documentation.** It is used when a flow is
saved, so a flow referencing a key you do not support fails at authoring time
rather than mid-conversation. Keep it accurate.

**`get()` is called during execution.** It is on the hot path for any flow that
branches on your data. Keep it cheap, and remember it receives the contact and
tenant it is being asked about — it must not read anything outside that tenant.

**The accessor belongs to the module, not to Core.** Core provides the registry;
you provide the answer.

See also [State namespaces](/extending/flow-nodes/state-namespaces) for how
`module.*` differs from the namespaces a handler may write.