# pg_trigram_similarity

Find similar strings using pg_trgm trigram matching. Returns similarity score (0-1). Default threshold 0.3; use lower (e.g., 0.1) for partial matches.

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

## Facts

- Tool: `pg_trigram_similarity`
- 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_trigram_similarity",
    "arguments": {}
  }
}
```

## Why pg_trigram_similarity is rated Low

This tool retrieves data (string similarity results) without side effects. It does not create, modify, delete data, execute arbitrary code, or trigger external operations. The threshold parameter controls matching sensitivity but does not alter underlying data. This is a classic Read operation — search/filter over existing content.

From the tool's own definition: "Tool description states it 'Find[s] similar strings' and 'Returns similarity score' — purely a query operation with no modification, deletion, or execution of external commands. The pg_trgm trigram matching is a built-in PostgreSQL text search function."

## Use case

AI agents call pg_trigram_similarity 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_trigram_similarity": {}
  }
}
```

## 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