Execute an EXPLAIN (FORMAT JSON) query to get PostgreSQL execution plan. Args: query: The SQL query to analyze conn_id: Connection ID previously obtained from the connect tool params: Parameters for the query (optional) Returns: Complete JSON-formatted execution plan
AI agents invoke pg_explain to trigger actions in Pg. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
This tool falls into the Execute category because it triggers external operations on a PostgreSQL database—specifically executing EXPLAIN commands whose effects (performance analysis, resource consumption during planning) depend on the query argument provided.
From the tool's definition The tool executes an EXPLAIN query against a PostgreSQL database. The description states 'Execute an EXPLAIN (FORMAT JSON) query' and accepts a 'query' parameter that is sent to the database.
Documented attack patterns abuse exactly the kind of access pg_explain gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Pg, and nothing reaches the server without passing your rules. This is the rule we recommend for pg_explain:
{
"version": "1",
"default": "deny",
"tools": {
"pg_explain": {
"limits": [
{
"counter": "pg_explain_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}pg_explain stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
Free to start. No card required.
Execute an EXPLAIN (FORMAT JSON) query to get PostgreSQL execution plan. Args: query: The SQL query to analyze conn_id: Connection ID previously obtained from the connect tool params: Parameters for the query (optional) Returns: Complete JSON-formatted execution plan. It is categorised as a Execute tool in the Pg MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Pg MCP server in PolicyLayer and add a rule for pg_explain: 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 Pg. Nothing to install.
pg_explain is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the pg_explain 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 pg_explain. 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.
pg_explain is provided by the Pg MCP server (stuzero/pg-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 5 Pg tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
5 Pg tools catalogued and risk-classified — across an index of 42,500+ MCP servers.