PostgreSQL_create_user
AI agents use PostgreSQL_create_user to create or update resources in Postgres — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Postgres environment.
Creating a user is a reversible Write operation—new user accounts can be deleted or modified. However, severity is elevated to 'high' because creating unauthorized database users could grant access to sensitive data, enable privilege escalation, or facilitate lateral movement within a database system. The tool affects database security posture materially.
From the tool's definition Tool name 'PostgreSQL_create_user' indicates creation of a database user account. Description is empty, but the name and server context (PostgreSQL database management) make the intent clear.
Documented attack patterns abuse exactly the kind of access PostgreSQL_create_user gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Postgres, and nothing reaches the server without passing your rules. This is the rule we recommend for PostgreSQL_create_user:
{
"version": "1",
"default": "deny",
"tools": {
"PostgreSQL_create_user": {
"limits": [
{
"counter": "postgresql_create_user_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}PostgreSQL_create_user 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.
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PostgreSQL_create_user. It is categorised as a Write tool in the Postgres MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Postgres MCP server in PolicyLayer and add a rule for PostgreSQL_create_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 Postgres. Nothing to install.
PostgreSQL_create_user 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 PostgreSQL_create_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 PostgreSQL_create_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.
PostgreSQL_create_user is provided by the Postgres MCP server (mukul975/postgres-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Postgres, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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239 Postgres tools catalogued and risk-classified — across an index of 43,000+ MCP servers.