List all Matrix rooms that the user has joined. Returns room IDs, names, and basic information about each room. Use this to discover which rooms are available before fetching messages. Returns: - List of rooms with room_id, name, topic, and member count - Use room_id with matrix_get_messages to r...
AI agents call matrix_list_rooms to retrieve information from Element MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool only retrieves and lists existing data (room metadata) without creating, modifying, deleting, executing code, or transferring funds. It is a pure read operation with minimal blast radius—discovery of room names and IDs an attacker already has access to in their own Matrix account.
From the tool's definition Tool name 'matrix_list_rooms' and description state it 'List all Matrix rooms' and 'discover which rooms are available', returning 'room_id, name, topic, and member count' with no modification capability. No side effects mentioned.
Attacks that exploit this kind of access
List all Matrix rooms that the user has joined. Returns room IDs, names, and basic information about each room. Use this to discover which rooms are available before fetching messages. Returns: - List of rooms with room_id, name, topic, and member count - Use room_id with matrix_get_messages to read messages. It is categorised as a Read tool in the Element MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Element MCP Server MCP server in PolicyLayer and add a rule for matrix_list_rooms: 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 Element MCP Server. Nothing to install.
matrix_list_rooms 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 matrix_list_rooms 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 matrix_list_rooms. 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.
matrix_list_rooms is provided by the Element MCP Server MCP server (rosquillas/element-mcp-server). 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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