# Choosing an Annotation Scheme

Source: https://www.potatoannotator.com/docs/guides/choosing-an-annotation-scheme

**The annotation scheme is the shape of the question you ask annotators. Pick it by asking what kind of answer you need: one category, several categories, a region of the item, a position on a scale, or a comparison between items.** Potato supports more than 30 annotation types; this guide narrows them down.

For the full list of options and their settings, see the [Annotation Schemes reference](/docs/core-concepts/annotation-schemes).

## A decision guide

| If you need… | Use this type | Example |
|---|---|---|
| Exactly one category | `radio` | Sentiment: positive / negative / neutral |
| Several categories at once | `multiselect` | Topics present in an article |
| A category from a long list | `select` (dropdown) | Country, language, ICD code |
| A region inside the text/audio | `span` | Named entities, error spans |
| A position on a scale | `likert` | Agreement, fluency, quality |
| A continuous value | `slider` | Confidence 0–100 |
| The better of two items | `pairwise` | Which model reply is better? |
| Best and worst of a set | `best_worst_scaling` | Rank translations by fluency |
| The same scale across many items | `multirate` | Rate each retrieved document |
| Multiple weighted criteria | `rubric_eval` | MT-Bench-style LLM scoring |
| A written answer | `text` | Justification, correction |

## Worked example: single vs. multiple labels

If categories are mutually exclusive, use `radio` so annotators must pick one:

```yaml
annotation_schemes:
  - annotation_type: radio
    name: stance
    description: "What stance does the post take?"
    labels: [Supports, Opposes, Neutral]
    sequential_key_binding: true
```

If an item can have several labels at once, use `multiselect` and set limits:

```yaml
annotation_schemes:
  - annotation_type: multiselect
    name: topics
    description: "Select every topic the article covers."
    labels: [Politics, Technology, Health, Sports, Business]
    min_selections: 1
    max_selections: 3
```

`sequential_key_binding: true` lets annotators press number keys instead of clicking, which speeds up large jobs.

## Combine schemes for richer tasks

You can stack several schemes on one screen, for example, a category plus a free-text reason. Pair them with conditional logic so the reason only appears when it is needed:

```yaml
annotation_schemes:
  - annotation_type: radio
    name: quality
    description: "Is this answer acceptable?"
    labels: [Good, Bad]
  - annotation_type: text
    name: reason
    description: "If Bad, briefly explain why."
    label_requirement:
      required: false
```

## Further reading

- [Text Annotation](/docs/guides/text-annotation) and [Span Annotation](/docs/guides/span-annotation)
- [Rating Scales](/docs/guides/rating-scales) and [Pairwise and Best–Worst Scaling](/docs/guides/pairwise-and-best-worst)
- [Writing Annotation Guidelines](/docs/guides/writing-annotation-guidelines)