# Validation Domain Model

A `Validation` extends `Tool` with pass/fail semantics. Validations are
always read-only (`writes=False`, `checkpointable=False`, `read_only=True`).

## Validation-Specific Fields

| Field              | Type                    | Default     | Description                              |
|--------------------|-------------------------|-------------|------------------------------------------|
| `mode`             | `ValidationMode`        | `required`  | Whether failure blocks execution         |
| `wraps`            | `str \| None`           | `None`      | Name of existing tool to wrap            |
| `transform`        | `str \| None`           | `None`      | Python code to transform wrapped output  |
| `argument_mapping` | `dict \| None`          | `None`      | Args for wrapped tool (only with wraps)  |

All fields from `Tool` are also available.

## Forced Constraints

When constructing a Validation, the following are always enforced:

- `tool_type` is forced to `ToolType.VALIDATION`
- `capability.read_only` is forced to `True`
- `capability.writes` is forced to `False`
- `capability.checkpointable` is forced to `False`

## Wraps Semantics

A Validation may wrap an existing Tool to reuse its implementation:

- When `wraps` is set, `source` must be `wrapped`
- When `wraps` is set, `code` must not be set (mutually exclusive)
- When `wraps` is set, `transform` is required
- `argument_mapping` is only valid when `wraps` is set

## Modes

| Mode            | Behavior                                        |
|-----------------|-------------------------------------------------|
| `required`      | Failure blocks the operation                    |
| `informational` | Failure is reported but does not block           |

## Class Methods

- `Validation.from_config(config: dict)` -- Create from a YAML config dict
  (auto-detects `source=wrapped` when `wraps` is present)
- `validation.as_cli_dict()` -- Stable ordered dict with validation fields

## CLI Management

```
agents validation add --config <file> [--update]
agents validation attach [--project <project>|--plan <plan_id>] <resource> <validation>
agents validation detach [--yes] <attachment_id>
```

Validations are listed and inspected via standard `agents tool` commands
with `--type validation` filter.