Context lookup: Parse a User-Agent header string into structured browser, OS, device type, and rendering-engine components. Use to identify client capabilities from a raw UA string, e.g. when analysing server logs or request headers; does not perform any network lookups — entirely local parsing. ...
Part of the Drwho Me developer tools server.
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AI agents invoke user_agent_parse to trigger processes or run actions in Drwho Me developer tools. Execute operations can have side effects beyond the immediate call -- triggering builds, sending notifications, or starting workflows. Rate limits and argument validation are essential to prevent runaway execution.
user_agent_parse can trigger processes with real-world consequences. An uncontrolled agent might start dozens of builds, send mass notifications, or kick off expensive compute jobs. PolicyLayer enforces rate limits and validates arguments to keep execution within safe bounds.
Execute tools trigger processes. Rate-limit and validate arguments to prevent unintended side effects.
{
"version": "1",
"default": "deny",
"tools": {
"user_agent_parse": {
"limits": [
{
"counter": "user_agent_parse_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}See the full Drwho Me developer tools policy for all 19 tools.
These attack patterns abuse exactly the kind of access user_agent_parse gives an agent. Each links to the full case and the policy that stops it:
Other execute tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.
Context lookup: Parse a User-Agent header string into structured browser, OS, device type, and rendering-engine components. Use to identify client capabilities from a raw UA string, e.g. when analysing server logs or request headers; does not perform any network lookups — entirely local parsing. Runs synchronously using the ua-parser-js library with no external calls. Returns a JSON object with browser.name, browser.version, os.name, os.version, device.type, device.vendor, and engine.name fields; unknown fields are empty strings.. It is categorised as a Execute tool in the Drwho Me developer tools MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Drwho Me developer tools MCP server in PolicyLayer and add a rule for user_agent_parse: 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 Drwho Me developer tools. Nothing to install.
user_agent_parse is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the user_agent_parse 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 user_agent_parse. 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.
user_agent_parse is provided by the Drwho Me developer tools MCP server (https://drwho.me/mcp/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 19 Drwho Me developer tools tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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