check_in_library
Preferred. Accepts the widest URI mix (track, album, episode, show, audiobook, artist, user, playlist) in one request. Check whether items are saved in or followed by the user — this tests LIBRARY-SAVED/FOLLOWED state, distinct from check_following_artists which only tests artist FOLLOW state. Re...
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What check_in_library does on Spotify
AI agents call check_in_library to retrieve information from Spotify without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Why check_in_library is rated Low
Queries user library and follow state without modifying data or triggering external actions.
From the tool's definition Check whether items are saved in or followed by the user. Returns a boolean per URI.
Attacks that exploit this kind of access
The rule that runs check_in_library safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Spotify, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For check_in_library, this is the rule to start with:
check_in_library is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Spotify, apply this rule, and every check_in_library call is checked against it from then on.
Questions about check_in_library
Preferred. Accepts the widest URI mix (track, album, episode, show, audiobook, artist, user, playlist) in one request. Check whether items are saved in or followed by the user — this tests LIBRARY-SAVED/FOLLOWED state, distinct from check_following_artists which only tests artist FOLLOW state. Returns a boolean per URI via Spotify. It is categorised as a Read tool in the Spotify MCP Server, which means it retrieves data without modifying state.
Register the Spotify MCP server in PolicyLayer and add a rule for check_in_library: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Spotify. Nothing to install.
check_in_library is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the check_in_library rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for check_in_library. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
check_in_library is provided by the Spotify MCP server (@novalux12/spotify-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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