Docs
chromia.com

ENTITY

auth_descriptor_signer

Represents a keypair that has access to an auth descriptor.

entity auth_descriptor_signer {
 key id: byte_array;
 key account_auth_descriptor: account_auth_descriptor;
}
key id: byte_array;

Either the pubkey or, for EVM signers, the EVM address (without 0x)

key account_auth_descriptor: account_auth_descriptor;

the auth descriptor this signer can access

Source