synapse/docs/application_services.md

Registering an Application Service

The registration of new application services depends on the homeserver used. In synapse, you need to create a new configuration file for your AS and add it to the list specified under the app_service_config_files config option in your synapse config.

For example:

app_service_config_files:
- /home/matrix/.synapse/<your-AS>.yaml

The format of the AS configuration file is as follows:

url: <base url of AS>
as_token: <token AS will add to requests to HS>
hs_token: <token HS will add to requests to AS>
sender_localpart: <localpart of AS user>
namespaces:
  users:  # List of users we're interested in
    - exclusive: <bool>
      regex: <regex>
      group_id: <group>
    - ...
  aliases: []  # List of aliases we're interested in
  rooms: [] # List of room ids we're interested in

exclusive: If enabled, only this application service is allowed to register users in its namespace(s). group_id: All users of this application service are dynamically joined to this group. This is useful for e.g user organisation or flairs.

See the spec for further details on how application services work.