List which users/agents/apps/runs currently hold memories.
AI agents call list_entities to retrieve information from Mem0 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 metadata about entities (users, agents, apps, runs) that have associated memories. It has no side effects, does not execute code, does not modify data, and does not delete anything. It is a read-only query operation.
From the tool's definition Tool name 'list_entities' and description 'List which users/agents/apps/runs currently hold memories' — a pure retrieval operation with no data modification or execution.
Attacks that exploit this kind of access
List which users/agents/apps/runs currently hold memories. It is categorised as a Read tool in the Mem0 MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Mem0 MCP Server MCP server in PolicyLayer and add a rule for list_entities: 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 Mem0 MCP Server. Nothing to install.
list_entities 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 list_entities 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 list_entities. 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.
list_entities is provided by the Mem0 MCP Server MCP server (mem0ai/mem0-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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