AI agents call list_schemas to retrieve information from 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 read-only operation on database metadata. It queries schema information and returns counts/sizes—classic database inspection with no side effects, no code execution, and no data creation/modification/deletion. It is appropriate for catalog operations and inventory tasks.
From the tool's definition Tool name 'list_schemas' and description 'List all schemas in the PostgreSQL database with table/view counts and total size' indicate a query operation that retrieves metadata without modification.
Attacks that exploit this kind of access
List all schemas in the PostgreSQL database with table/view counts and total size. It is categorised as a Read tool in the Server MCP Server, which means it retrieves data without modifying state.
Register the 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 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 Server MCP server (@nest-mcp/server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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