# query

Execute a read-only SQL query against the PostgreSQL database. Use this for SELECT, SHOW, EXPLAIN statements.

Agent View of the PolicyLayer registry record for `query`. HTML page: https://policylayer.com/tools/aeiyannn-postgree-mcp/query

## Facts

- Tool: `query`
- Server: PostgreSQL MCP Server (`aeiyannn/postgree-mcp`) — https://policylayer.com/tools/aeiyannn-postgree-mcp.md
- Homepage: https://github.com/aeiyannn/postgree-mcp
- Risk category: Read (Low risk)
- Registry record: grade C, identity unverified
- Server rate-limited: no
- Parameters: 0
- Recommended policy verdict: Allowed

## Example call (MCP tools/call, JSON-RPC 2.0)

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "query",
    "arguments": {}
  }
}
```

## Why query is rated Low

This tool is constrained to read-only SQL operations (SELECT, SHOW, EXPLAIN) with no data modification, deletion, or external side effects. The main risk is information disclosure if the database contains sensitive data, but the tool itself cannot modify state. Severity is low because the blast radius is limited to data exposure rather than system compromise or data loss.

From the tool's own definition: "Tool description explicitly states 'Execute a read-only SQL query' and restricts usage to 'SELECT, SHOW, EXPLAIN statements' which are non-destructive query operations."

## Use case

AI agents call query to retrieve information from PostgreSQL MCP Server without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.

## Recommended policy (PolicyLayer)

Verdict: **Allowed**. Enforced by the PolicyLayer MCP gateway (https://policylayer.com/mcp-gateway) before a call reaches PostgreSQL MCP Server:

```json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "query": {}
  }
}
```

## Other tools on PostgreSQL MCP Server (4)

- `execute` — Destructive — https://policylayer.com/tools/aeiyannn-postgree-mcp/execute.md
- `describe_table` — Read — https://policylayer.com/tools/aeiyannn-postgree-mcp/describe-table.md
- `list_schemas` — Read — https://policylayer.com/tools/aeiyannn-postgree-mcp/list-schemas.md
- `list_tables` — Read — https://policylayer.com/tools/aeiyannn-postgree-mcp/list-tables.md

## For agents

This record is a snapshot. Live verdicts and the full registry:

- Check every server in your MCP config at once: `npx -y policylayer stack`
- Vet a server before you add it: install the mcp-precheck skill — `npx skills add https://policylayer.com` (skill text: https://policylayer.com/skill.md)
- Query the registry over MCP: endpoint `https://api.policylayer.com/mcp` — tools `check_mcp_server`, `check_mcp_stack`, `check_tool`, `search_registry`, `get_change_events`

---

Source: the PolicyLayer MCP registry — one continuously verified record per MCP server. Full record: https://policylayer.com/registry?q=aeiyannn-postgree-mcp · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/aeiyannn-postgree-mcp