List all schemas in the PostgreSQL database.
AI agents call list_schemas to retrieve information from Postgres without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves schema information from the database with no side effects. It is a straightforward metadata query operation, consistent with the 'Read' category for tools that retrieve or query data. The server description emphasizes 'read-only mode by default,' and this tool exemplifies that design.
From the tool's definition Tool name 'list_schemas' and description 'List all schemas in the PostgreSQL database' indicate a read-only query operation that retrieves metadata without modifying or executing code.
Documented attack patterns abuse exactly the kind of access list_schemas 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 list_schemas:
{
"version": "1",
"default": "deny",
"tools": {
"list_schemas": {}
}
}list_schemas is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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List all schemas in the PostgreSQL database. It is categorised as a Read tool in the Postgres MCP Server, which means it retrieves data without modifying state.
Register the Postgres MCP server in PolicyLayer and add a rule for list_schemas: 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.
list_schemas 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_schemas 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_schemas. 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_schemas is provided by the Postgres MCP server (javimaligno/postgres_mcp). 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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14 Postgres tools catalogued and risk-classified — across an index of 43,000+ MCP servers.