> For the complete documentation index, see [llms.txt](https://developers.wiki.resourcefulbees.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developers.wiki.resourcefulbees.com/recipes/mutation-entry.md).

# Mutation Entry

Each entry in a `resourcefulbees:mutation` recipe maps one input mutation predicate to one or more possible output mutations.

## Fields

| Field     | Type                      | Required | Default | Notes                                                                    |
| --------- | ------------------------- | -------- | ------- | ------------------------------------------------------------------------ |
| `input`   | Mutation object           | Yes      | —       | Uses the built-in mutation dispatch described below.                     |
| `outputs` | array of Mutation objects | Yes      | —       | Plain list of output mutation objects; there is no outer weight wrapper. |

An empty `outputs` array is structurally possible if accepted by the list codec, but is not useful for gameplay.

## Mutation dispatch

Mutation objects are dispatched by their required `type` field. Built-in values are:

* `item`
* `block`
* `fluid`
* `entity`

All built-in mutation objects also support the common fields below.

| Field    | Type   | Required | Default | Range               |
| -------- | ------ | -------- | ------- | ------------------- |
| `chance` | number | No       | `1.0`   | `0.0` through `1.0` |
| `weight` | number | No       | `10.0`  | `>= 0`              |

`chance` determines whether the mutation succeeds when selected. `weight` participates in weighted selection where multiple candidates are available.

## Item mutation

```json
{
  "type": "item",
  "item": {
    "id": "minecraft:diamond"
  },
  "chance": 1.0,
  "weight": 10.0
}
```

| Field    | Type                      | Required | Default |
| -------- | ------------------------- | -------- | ------- |
| `type`   | string                    | Yes      | `item`  |
| `item`   | Restricted item predicate | Yes      | —       |
| `chance` | number                    | No       | `1.0`   |
| `weight` | number                    | No       | `10.0`  |

The item predicate requires `id` and may additionally contain `components`, `durability`, and `count` constraints.

## Block mutation

```json
{
  "type": "block",
  "block": {
    "id": "minecraft:diamond_block"
  }
}
```

| Field    | Type                       | Required | Default |
| -------- | -------------------------- | -------- | ------- |
| `type`   | string                     | Yes      | `block` |
| `block`  | Restricted block predicate | Yes      | —       |
| `chance` | number                     | No       | `1.0`   |
| `weight` | number                     | No       | `10.0`  |

The block predicate requires `id` and may additionally constrain `components`, `location`, or block `properties`.

## Fluid mutation

```json
{
  "type": "fluid",
  "fluid": "minecraft:water"
}
```

| Field    | Type             | Required | Default |
| -------- | ---------------- | -------- | ------- |
| `type`   | string           | Yes      | `fluid` |
| `fluid`  | fluid identifier | Yes      | —       |
| `chance` | number           | No       | `1.0`   |
| `weight` | number           | No       | `10.0`  |

## Entity mutation

```json
{
  "type": "entity",
  "entity": {
    "type": "minecraft:cow"
  }
}
```

| Field    | Type                        | Required | Default  |
| -------- | --------------------------- | -------- | -------- |
| `type`   | string                      | Yes      | `entity` |
| `entity` | Restricted entity predicate | Yes      | —        |
| `chance` | number                      | No       | `1.0`    |
| `weight` | number                      | No       | `10.0`   |

The entity predicate requires an entity `type` and may additionally include location, effects, NBT, flags, and target constraints.