Set a custom or random user agent string
AI agents use set_user_agent to create or update resources in Pydoll — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Pydoll environment.
This tool modifies the browser's user agent configuration, which is a reversible write operation. It changes browser settings that affect how the browser identifies itself to web servers. While it can be used to disguise automated browsing or evade detection, the action itself is a configuration write. Misuse could facilitate bypassing bot detection or impersonation, hence medium severity.
From the tool's definition Set a custom or random user agent string
Documented attack patterns abuse exactly the kind of access set_user_agent gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Pydoll, and nothing reaches the server without passing your rules. This is the rule we recommend for set_user_agent:
{
"version": "1",
"default": "deny",
"tools": {
"set_user_agent": {
"limits": [
{
"counter": "set_user_agent_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}set_user_agent 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.
Free to start. No card required.
Set a custom or random user agent string. It is categorised as a Write tool in the Pydoll MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Pydoll MCP server in PolicyLayer and add a rule for set_user_agent: 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 Pydoll. Nothing to install.
set_user_agent 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 set_user_agent 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 set_user_agent. 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.
set_user_agent is provided by the Pydoll MCP server (jinsongroh/pydoll-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Pydoll, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
57 Pydoll tools catalogued and risk-classified — across an index of 43,000+ MCP servers.