# lehmer_code

Convert between permutations and Lehmer codes, compute permutation rank and unrank.

Agent View of the PolicyLayer registry record for `lehmer_code`. HTML page: https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/lehmer-code

## Facts

- Tool: `lehmer_code`
- Server: UnClick (`@unclick/mcp-server`) — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server.md
- Install: `npx -y @unclick/mcp-server`
- Homepage: https://github.com/malamutemayhem/unclick-agent-native-endpoints.git
- Risk category: Read (Low risk)
- Registry record: grade F, identity unverified
- Server rate-limited: no
- Parameters: 3
- Recommended policy verdict: Allowed

## Parameters

| Parameter | Type | Required | Description |
| --- | --- | --- | --- |
| `n` | number | no | Permutation size for unranking (use with rank) |
| `rank` | number | no | Lexicographic rank to decode (use with n) |
| `permutation` | array | no | Permutation of [0..n-1] to encode |

Parameters from the server's own tool schema.

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

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

## Why lehmer_code is rated Low

Lehmer code conversion and permutation ranking are stateless mathematical algorithms. The tool reads input parameters and returns computed results without creating, modifying, deleting, or executing any external operations. This is a straightforward Read-category utility with minimal security risk.

From the tool's own definition: "Tool description states 'Convert between permutations and Lehmer codes, compute permutation rank and unrank' — these are pure mathematical computations with no side effects, data retrieval, modification, or external operations."

## Use case

AI agents call lehmer_code to retrieve information from UnClick 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 UnClick:

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

## Other tools on UnClick (1661)

- `delete_todo` — Destructive — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/delete-todo.md
- `email_delete` — Destructive — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/email-delete.md
- `file_sync_prune` — Destructive — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/file-sync-prune.md
- `pinecone_delete_vectors` — Destructive — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/pinecone-delete-vectors.md
- `telegram_manage_chat` — Destructive — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/telegram-manage-chat.md
- `upstash_redis_del` — Destructive — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/upstash-redis-del.md
- `vault_action` — Destructive — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/vault-action.md
- `vercel_delete_env` — Destructive — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/vercel-delete-env.md
- `ackermann` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/ackermann.md
- `anthropic_create_message` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/anthropic-create-message.md
- `avl_tree` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/avl-tree.md
- `baby_giant_step` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/baby-giant-step.md
- `bellman_ford` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/bellman-ford.md
- `bezier_curve` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/bezier-curve.md
- `bitmask_ops` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/bitmask-ops.md
- `bitwise_calc` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/bitwise-calc.md
- `bloom_filter` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/bloom-filter.md
- `bluesky_action` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/bluesky-action.md
- `burrows_wheeler` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/burrows-wheeler.md
- `cartesian_tree` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/cartesian-tree.md
- `chromatic_number` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/chromatic-number.md
- `circleci_trigger_pipeline` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/circleci-trigger-pipeline.md
- `cohere_chat` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/cohere-chat.md
- `cohere_classify` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/cohere-classify.md
- `cohere_generate` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/cohere-generate.md
- `commonsensepass_check` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/commonsensepass-check.md
- `complex_calc` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/complex-calc.md
- `compliancepass_run` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/compliancepass-run.md
- `convex_hull_3d` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/convex-hull-3d.md
- `convolution` — Execute — https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server/convolution.md
- …and 1631 more: https://policylayer.com/tools/io-github-malamutemayhem-unclick-mcp-server.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-malamutemayhem-unclick-mcp-server · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/io-github-malamutemayhem-unclick-mcp-server