# pg_list_constraints

List table constraints (primary keys, foreign keys, unique, check).

Agent View of the PolicyLayer registry record for `pg_list_constraints`. HTML page: https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-list-constraints

## Facts

- Tool: `pg_list_constraints`
- Server: PostgreSQL MCP Server (`@neverinfamous/postgres-mcp`) — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp.md
- Install: `npx -y @neverinfamous/postgres-mcp`
- Homepage: https://github.com/neverinfamous/postgresql-mcp.git
- 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": "pg_list_constraints",
    "arguments": {}
  }
}
```

## Why pg_list_constraints is rated Low

This tool performs a read-only query of database schema metadata (constraint definitions). It has no side effects, cannot modify data, and poses minimal risk even if an AI agent calls it with any arguments. It aligns with the Read category definition: 'retrieves or queries data; no side effects (search, list, get, fetch)'.

From the tool's own definition: "Tool name 'pg_list_constraints' and description 'List table constraints' indicate a retrieval operation that queries constraint metadata without modifying or executing any operations."

## Use case

AI agents call pg_list_constraints 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": {
    "pg_list_constraints": {}
  }
}
```

## Other tools on PostgreSQL MCP Server (273)

- `pg_cascade_simulator` — Destructive — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-cascade-simulator.md
- `pg_cron_cleanup_history` — Destructive — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-cron-cleanup-history.md
- `pg_cron_unschedule` — Destructive — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-cron-unschedule.md
- `pg_detach_partition` — Destructive — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-detach-partition.md
- `pg_doc_drop_collection` — Destructive — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-doc-drop-collection.md
- `pg_doc_remove` — Destructive — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-doc-remove.md
- `pg_drop_index` — Destructive — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-drop-index.md
- `pg_drop_schema` — Destructive — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-drop-schema.md
- `pg_drop_sequence` — Destructive — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-drop-sequence.md
- `pg_drop_table` — Destructive — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-drop-table.md
- `pg_drop_view` — Destructive — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-drop-view.md
- `pg_kcache_reset` — Destructive — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-kcache-reset.md
- `pg_migration_rollback` — Destructive — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-migration-rollback.md
- `pg_partman_set_retention` — Destructive — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-partman-set-retention.md
- `pg_reset_stats` — Destructive — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-reset-stats.md
- `pg_role_drop` — Destructive — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-role-drop.md
- `pg_text_normalize` — Destructive — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-text-normalize.md
- `pg_truncate` — Destructive — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-truncate.md
- `pg_analyze` — Execute — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-analyze.md
- `pg_analyze_query_indexes` — Execute — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-analyze-query-indexes.md
- `pg_buffer` — Execute — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-buffer.md
- `pg_cancel_backend` — Execute — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-cancel-backend.md
- `pg_cluster` — Execute — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-cluster.md
- `pg_cron_create_extension` — Execute — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-cron-create-extension.md
- `pg_cron_schedule` — Execute — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-cron-schedule.md
- `pg_cron_schedule_in_database` — Execute — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-cron-schedule-in-database.md
- `pg_explain_analyze` — Execute — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-explain-analyze.md
- `pg_geo_cluster` — Execute — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-geo-cluster.md
- `pg_geo_transform` — Execute — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-geo-transform.md
- `pg_geometry_transform` — Execute — https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp/pg-geometry-transform.md
- …and 243 more: https://policylayer.com/tools/io-github-neverinfamous-postgres-mcp.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=io-github-neverinfamous-postgres-mcp · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/io-github-neverinfamous-postgres-mcp