no-format

Id

@azure-tools/typespec-azure-core/no-format

Azure services should not use the @format decorator.

Using the @format decorator is disallowed. While in OpenAPI format: was used to both represent a known string format and a more precise type, in TypeSpec @format is only meant to represent a known pattern for a string. This means that using @format would result in a string type with some validation.

Impact

• Area: API, SDK

@format may specify an invalid or non-standard format.

Mapping of format to types

Format	Type
int32	int32
uri	url
url	url
uuid	Azure.Core.uuid
eTag	Azure.Core.eTag
arm-id	Azure.Core.armResourceIdentifier
ipv4	Azure.Core.ipV4Address
ipv6	Azure.Core.ipV6Address
ipv6	Azure.Core.azureLocation

Examples

❌ Incorrect

model Pet {
  @format("uuid")
  id: string;
}

✅ Correct

model Pet {
  id: Azure.Core.uuid;
}

Suppression

Suppression is acceptable when a valid format is used. Prefer standard types (which apply the correct wire format automatically), or @encode when a non-standard format such as base64url is required.