Expand a short URL to its original long URL
AI agents call expand_url to retrieve information from YOURLS-MCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool only queries data (the original URL from a shortened reference) and returns it without side effects. It does not create, modify, delete, or execute operations. It is a pure read operation similar to a database lookup or API query.
From the tool's definition Tool description states 'Expand a short URL to its original long URL' — a retrieval operation with no modification, deletion, or execution of code. The function retrieves and returns the long URL corresponding to a short URL.
Attacks that exploit this kind of access
Expand a short URL to its original long URL. It is categorised as a Read tool in the YOURLS-MCP MCP Server, which means it retrieves data without modifying state.
Register the YOURLS- MCP server in PolicyLayer and add a rule for expand_url: 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 YOURLS-MCP. Nothing to install.
expand_url 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 expand_url 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 expand_url. 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.
expand_url is provided by the YOURLS- MCP server (kesslerio/yourls-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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