AI agents call list_storage_buckets to retrieve information from PostgREST without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool only queries and returns information about existing storage buckets without modifying, deleting, executing operations, or moving financial resources. It is a straightforward read operation with minimal security risk—the blast radius is limited to information disclosure of bucket metadata.
From the tool's definition Tool name 'list_storage_buckets' and description 'Lists all storage buckets in a Supabase project' indicate a retrieval operation with no side effects.
Documented attack patterns abuse exactly the kind of access list_storage_buckets gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and PostgREST, and nothing reaches the server without passing your rules. This is the rule we recommend for list_storage_buckets:
{
"version": "1",
"default": "deny",
"tools": {
"list_storage_buckets": {}
}
}list_storage_buckets is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Lists all storage buckets in a Supabase project. It is categorised as a Read tool in the PostgREST MCP Server, which means it retrieves data without modifying state.
Register the PostgREST MCP server in PolicyLayer and add a rule for list_storage_buckets: 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 PostgREST. Nothing to install.
list_storage_buckets 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 list_storage_buckets 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 list_storage_buckets. 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.
list_storage_buckets is provided by the PostgREST MCP server (supabase/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 32 PostgREST tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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32 PostgREST tools catalogued and risk-classified — across an index of 42,500+ MCP servers.