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>
    - ...
  aliases: []  # List of aliases we're interested in
  rooms: [] # List of room ids we're interested in

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