List all categories visible to the current user. Returns category names and topic counts. Useful for discovering where to post or search.
AI agents call discourse_list_categories to retrieve information from Discourse MCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves and displays metadata about forum categories without modifying, deleting, or executing any operations. It has no side effects and presents no risk of data loss, unauthorized execution, or financial impact. The blast radius of misuse is negligible—an agent can only discover existing category information already visible to the user.
From the tool's definition Tool name and description: 'List all categories visible to the current user. Returns category names and topic counts.' The verb 'list' and the retrieval-only nature (returns data without modification) confirm this is a read operation.
Attacks that exploit this kind of access
List all categories visible to the current user. Returns category names and topic counts. Useful for discovering where to post or search. It is categorised as a Read tool in the Discourse MCP MCP Server, which means it retrieves data without modifying state.
Register the Discourse MCP server in PolicyLayer and add a rule for discourse_list_categories: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Discourse MCP. Nothing to install.
discourse_list_categories is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the discourse_list_categories rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for discourse_list_categories. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
discourse_list_categories is provided by the Discourse MCP server (king-of-the-grackles/discourse-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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