# list_databases

Discover databases visible/connectable to the connected user (FR-002a)

Agent View of the PolicyLayer registry record for `list_databases`. HTML page: https://policylayer.com/tools/allensandiego-postgres-mcp-server/list-databases

## Facts

- Tool: `list_databases`
- Server: Postgres (`@allensandiego/postgres-mcp-server`) — https://policylayer.com/tools/allensandiego-postgres-mcp-server.md
- Install: `npx -y @allensandiego/postgres-mcp-server`
- Homepage: https://www.npmjs.com/package/@allensandiego/postgres-mcp-server
- Risk category: Read (Low risk)
- Registry record: grade F, 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": "list_databases",
    "arguments": {}
  }
}
```

## Why list_databases is rated Low

Even though list_databases only reads data, uncontrolled read access leaks sensitive information and racks up API costs: an agent caught in a retry loop can make thousands of calls a minute without anyone noticing.

## Use case

AI agents call list_databases to retrieve information from Postgres 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 Postgres:

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

## Other tools on Postgres (7)

- `run_query` — Execute — https://policylayer.com/tools/allensandiego-postgres-mcp-server/run-query.md
- `run_write_query` — Execute — https://policylayer.com/tools/allensandiego-postgres-mcp-server/run-write-query.md
- `describe_table` — Read — https://policylayer.com/tools/allensandiego-postgres-mcp-server/describe-table.md
- `list_permissions` — Read — https://policylayer.com/tools/allensandiego-postgres-mcp-server/list-permissions.md
- `list_roles` — Read — https://policylayer.com/tools/allensandiego-postgres-mcp-server/list-roles.md
- `list_tables` — Read — https://policylayer.com/tools/allensandiego-postgres-mcp-server/list-tables.md
- `set_role` — Write — https://policylayer.com/tools/allensandiego-postgres-mcp-server/set-role.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=allensandiego-postgres-mcp-server · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/allensandiego-postgres-mcp-server