# list_categories

Enumerate the full category tree for browsing GallanDigital's marketplace. Read-only, no authentication required (public endpoint, IP rate-limited), no parameters. Returns an array of categories, each with id, name, slug, description, parent_id, level, and display_order. Use first when browsing by category rather than searching by keyword, or to get valid category_slug values for search.

Agent View of the PolicyLayer registry record for `list_categories`. HTML page: https://policylayer.com/tools/com-gallandigital-marketplace/list-categories

## Facts

- Tool: `list_categories`
- Server: Marketplace (`https://gallandigital.com/api/mcp`) — https://policylayer.com/tools/com-gallandigital-marketplace.md
- Homepage: https://github.com/ZWingett/gallandigital-marketplace
- Risk category: Read (Low risk)
- Registry record: grade C, identity unverified
- Server auth posture: open
- 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_categories",
    "arguments": {}
  }
}
```

## Why list_categories is rated Low

This tool retrieves and lists public marketplace category metadata. It performs no modifications, deletions, or external executions. The absence of authentication and explicit 'read-only' designation confirm it is a simple enumeration endpoint. Low severity because exposure of category structure is unlikely to cause harm even if misused by an AI agent.

From the tool's own definition: "Tool description explicitly states 'Read-only', 'no authentication required', and it 'Enumerate[s] the full category tree' and 'Returns an array of categories'. These are all characteristics of a data retrieval operation with no side effects."

## Use case

AI agents call list_categories to retrieve information from Marketplace 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 Marketplace:

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

## Other tools on Marketplace (4)

- `fetch` — Read — https://policylayer.com/tools/com-gallandigital-marketplace/fetch.md
- `get_contributor_profile` — Read — https://policylayer.com/tools/com-gallandigital-marketplace/get-contributor-profile.md
- `get_deployment_guidance` — Read — https://policylayer.com/tools/com-gallandigital-marketplace/get-deployment-guidance.md
- `search` — Read — https://policylayer.com/tools/com-gallandigital-marketplace/search.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=com-gallandigital-marketplace · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/com-gallandigital-marketplace