List all tables with their columns, types, and constraints for a given schema (default: public)
AI agents call schema to retrieve information from Postgresql without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This is a pure schema inspection tool that retrieves database metadata without side effects. Although it operates on a PostgreSQL server with full read-write capabilities, the schema tool itself only queries structural information and poses minimal risk—it merely helps understand database layout.
From the tool's definition Tool lists tables, columns, types, and constraints—retrieval operations only. Description explicitly states 'List all tables' with no modification, deletion, or execution verbs. Returns metadata about schema structure.
Attacks that exploit this kind of access
List all tables with their columns, types, and constraints for a given schema (default: public). It is categorised as a Read tool in the Postgresql MCP Server, which means it retrieves data without modifying state.
Register the Postgresql MCP server in PolicyLayer and add a rule for schema: 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. Nothing to install.
schema 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 schema 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 schema. 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.
schema is provided by the Postgresql MCP server (sarmadparvez/postgresql-mcp). 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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