List schemas (excludes system schemas by default).
AI agents call list_schemas to retrieve information from PostgreSQL SSH MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs a metadata query to list database schemas. It has no side effects, does not modify data, and does not execute code or commands. The exclusion of system schemas by default is a safety-conscious design choice. The blast radius of misuse is minimal—listing schemas reveals structural information about the database but no actual data or ability to cause harm. This is a standard Read operation.
From the tool's definition Tool name 'list_schemas' and description 'List schemas (excludes system schemas by default)' indicate a pure read operation that retrieves and enumerates schema metadata without modification or execution.
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 PostgreSQL SSH MCP Server, 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 schemas (excludes system schemas by default). It is categorised as a Read tool in the PostgreSQL SSH MCP Server MCP Server, which means it retrieves data without modifying state.
Register the PostgreSQL SSH MCP Server 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 PostgreSQL SSH MCP Server. 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 PostgreSQL SSH MCP Server MCP server (zlash65/postgresql-ssh-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from PostgreSQL SSH MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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12 PostgreSQL SSH MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.