# Action fields
URL: https://docs.awellhealth.com/docs/extensions/action-fields

> For the complete documentation index, see [llms.txt](https://docs.awellhealth.com/llms.txt).



Action fields are how a care flow author configures an action in Awell Studio: the interface between an
extension and a non-engineer.

## What each field declares [#what-each-field-declares]

A field declares its key, label, description, type, and whether it's required.

Write the label and description for someone who doesn't know the API; they're all the author has to go
on. A field called `dest_num` with no description will be filled in wrongly.

## The available field types [#the-available-field-types]

| Type            | What the author gets                      |
| --------------- | ----------------------------------------- |
| `string`        | A single line of text                     |
| `text`          | Longer, multi-line text                   |
| `numeric`       | A number                                  |
| `boolean`       | A toggle                                  |
| `date`          | A date picker                             |
| `html`          | Rich text, for content that gets rendered |
| `json`          | A JSON value, for structured input        |
| `string_array`  | A list of text values                     |
| `numeric_array` | A list of numbers                         |

Pick the narrowest type that fits. A boolean can't be filled in wrongly the way a string can, and a
`date` field avoids parsing arbitrary date formats.

Reach for `json` last: it accepts any value, including a wrong one, and Studio gives the author no help
filling it in. Use it where the shape genuinely varies.

A `string` field can also carry a set of options, so the author picks from a list instead of typing. Do
that whenever the valid values are known: 74 fields across today's marketplace extensions do.

## Fields usually hold variables, not literals [#fields-usually-hold-variables-not-literals]

Authors can put [variables](/docs/design-care-flows/use-variables-in-your-actions) into field values, so
a field can carry patient-specific data at run time rather than a fixed value. Design for that: a "phone
number" field will usually hold a variable rather than a literal number.

## Next steps [#next-steps]

**Next:** [The onEvent function](/docs/extensions/on-event), where the field values arrive.