# Credential Definitions

An Anoncreds credential definition, represented by `AnoncredsCredDef`, enables the cloud agent to issue credentials from a specific Anoncreds [schema](https://docs.sudoplatform.com/guides/decentralized-identity/cloud-agent/cloud-agent-admin-api/credentials/anoncreds-credentials/schemas).

Anoncreds credential definitions are written to the ledger, and therefore cannot be modified or deleted once created. However, it is possible for multiple credential definitions to reference a single schema.

## Create an Anoncreds credential definition

The cloud agent creates a new `AnoncredsCredDef` and writes it permanently to the ledger. The `schemaId` param references an Anoncreds schema which must be already written to the ledger. The `isRevocable` param determines whether credentials issued using this credential definition can be revoked.

```graphql
mutation MyMutation {
  createAnoncredsCredDef(
    args: {
      schemaId: "Hoh1tsuYFJxqsuJ5vVjxuL:2:MySchema:1.0"
      tag: "MyCredDefTag"
      isRevocable: false
    }
  ) {
    id
  }
}
```

## View Anoncreds credential definitions

View Anoncreds credential definitions which are created by the cloud agent, with pagination and filtering options. Returns a `nextToken` which can be passed into the same query in order to fetch subsequent pages.

The `AnoncredsCredDef` type provides the option to resolve its associated `AnoncredsSchema` within a single operation.

```graphql
query MyQuery {
  anoncredsCredDefs(
    page: {
      nextToken: null
    }
    filter: {}
  ) {
    items {
      id
      schemaId
      schema {
        name
        version
        attributeNames
      }
      tag
      isRevocable
    }
    nextToken
  }
}
```

Alternatively, view a single Anoncreds credential definition, referenced by its unique ID.

```graphql
query MyQuery {
  anoncredsCredDef(
    credDefId: "Hoh1tsuYFJxqsuJ5vVjxuL:3:CL:3050:MyCredDefTag"
  ) {
    id
    schemaId
    schema {
      name
      version
      attributeNames
    }
    tag
    isRevocable
  }
}
```