AI agents call explain_query 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 query execution plans for analysis and optimization purposes. EXPLAIN statements are non-destructive, produce no side effects, and only return metadata about how PostgreSQL would execute a query. It fits squarely in the Read category alongside other tools like list_tables, describe_table, and get_table_stats mentioned as siblings on this read-optimized server.
From the tool's definition Tool is named 'explain_query' and described as retrieving 'the EXPLAIN plan for a SQL query.' EXPLAIN is a read-only SQL command that analyzes query execution without modifying data.
Attacks that exploit this kind of access
Get the EXPLAIN plan for a SQL query. 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 explain_query: 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.
explain_query 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 explain_query 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 explain_query. 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.
explain_query is provided by the Postgres MCP server (madhurprash/postgres-mcp-agentcore). 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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