AI agents call memory_diff to retrieve information from Mementos without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
memory_diff is a comparison/query tool that only retrieves and displays version history information. It has no side effects, creates no data, executes no code, and causes no irreversible changes. This is a classic Read category tool with minimal security risk.
From the tool's definition Tool description states it 'Show[s] what changed' and 'Compares value, importance, scope' between versions. These are read-only operations that retrieve and display differences without modifying, creating, or deleting any data.
Attacks that exploit this kind of access
Show what changed between two versions of a memory. Compares value, importance, scope. Omit v1/v2 to diff the two most recent versions. It is categorised as a Read tool in the Mementos MCP Server, which means it retrieves data without modifying state.
Register the Mementos MCP server in PolicyLayer and add a rule for memory_diff: 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 Mementos. Nothing to install.
memory_diff 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 memory_diff 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 memory_diff. 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.
memory_diff is provided by the Mementos MCP server (@hasna/mementos). 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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