navidrome/core/agents/README.md

This folder abstracts metadata lookup into "agents". Each agent can be implemented to get as much info as the external source provides, by using a granular set of interfaces (see interfaces).

A new agent must comply with these simple implementation rules:

1. Implement the AgentName() method. It just returns the name of the agent for logging purposes.
2. Implement one or more of the *Retriever() interfaces. That's where the agent's logic resides.
3. Register itself (in its init() function).

For an agent to be used it needs to be listed in the Agents config option (default is "lastfm,spotify"). The order dictates the priority of the agents

For a simple Agent example, look at the placeholders agent source code.