AI agents use follow_artists_or_users to create or update resources in PersonalizationMCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your PersonalizationMCP environment.
Following artists or users creates a new relationship/subscription on a platform (e.g., Spotify), which is a reversible write action. It modifies account state but can be undone by unfollowing. Misuse could result in unwanted follows across many accounts, hence medium severity.
From the tool's definition Follow artists or users
Documented attack patterns abuse exactly the kind of access follow_artists_or_users gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and PersonalizationMCP, and nothing reaches the server without passing your rules. This is the rule we recommend for follow_artists_or_users:
{
"version": "1",
"default": "deny",
"tools": {
"follow_artists_or_users": {
"limits": [
{
"counter": "follow_artists_or_users_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}follow_artists_or_users stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Follow artists or users. It is categorised as a Write tool in the PersonalizationMCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Personalization MCP server in PolicyLayer and add a rule for follow_artists_or_users: 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 PersonalizationMCP. Nothing to install.
follow_artists_or_users is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the follow_artists_or_users 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 follow_artists_or_users. 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.
follow_artists_or_users is provided by the Personalization MCP server (yangliangwei/personalizationmcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 88 PersonalizationMCP tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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88 PersonalizationMCP tools catalogued and risk-classified — across an index of 42,500+ MCP servers.