AI agents call list_comments to retrieve information from Youtube without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool queries and retrieves existing comment data from a video without modifying, deleting, or executing operations. It is a read-only operation with minimal blast radius—even if misused by an AI agent, it only exposes publicly or semi-publicly available comment data. The quota cost (1 unit) is typical for read operations on the YouTube API.
From the tool's definition Tool name 'list_comments' and description 'List top-level comments on a video' indicate retrieval of data with no side effects.
Attacks that exploit this kind of access
List top-level comments on a video. Costs 1 quota unit. It is categorised as a Read tool in the Youtube MCP Server, which means it retrieves data without modifying state.
Register the Youtube MCP server in PolicyLayer and add a rule for list_comments: 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 Youtube. Nothing to install.
list_comments 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 list_comments 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 list_comments. 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.
list_comments is provided by the Youtube MCP server (kpfitzgerald/youtube-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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