AI agents call get_captions 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 retrieves caption track information from a video without modifying any data or triggering side effects. It is a pure data retrieval operation, fitting the Read category. The quota cost is a resource consumption metric but does not change the nature of the operation. No destructive, financial, or code execution implications exist.
From the tool's definition The tool 'get_captions' is described as listing available caption tracks for a video. The verb 'list' and the action of retrieving caption metadata are read-only operations with no data modification, creation, deletion, or execution of external operations.
Attacks that exploit this kind of access
List available caption tracks for a video. Costs 200 quota units to download. 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 get_captions: 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.
get_captions 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 get_captions 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 get_captions. 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.
get_captions 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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