AI agents invoke impersonate_user to trigger actions in PocketBase MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
Impersonation is an Execute-class action that assumes another user's identity and session, enabling an AI agent to perform arbitrary actions on behalf of that user. While it doesn't directly delete data or move money, it is a privilege escalation mechanism with critical blast radius: a misuse could bypass access controls and allow unauthorized operations across the entire system under a different user's identity.
From the tool's definition 'Impersonate another user (admin only)' — triggers an authentication context switch, granting the caller the identity and permissions of another user
Risk signalsAdmin/system-level operation
Documented attack patterns abuse exactly the kind of access impersonate_user gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and PocketBase MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for impersonate_user:
{
"version": "1",
"default": "deny",
"tools": {
"impersonate_user": {
"limits": [
{
"counter": "impersonate_user_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}impersonate_user stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
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Impersonate another user (admin only). It is categorised as a Execute tool in the PocketBase MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the PocketBase MCP Server MCP server in PolicyLayer and add a rule for impersonate_user: 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 PocketBase MCP Server. Nothing to install.
impersonate_user 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 impersonate_user 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 impersonate_user. 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.
impersonate_user is provided by the PocketBase MCP Server MCP server (mrwyndham/pocketbase-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from PocketBase MCP Server, 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.
24 PocketBase MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.