AI agents call memory_similar to retrieve information from Rekal without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The tool appears to query similar memories from local SQLite storage—a read operation with no side effects. While the description is empty (lowering confidence slightly), the naming pattern and server's stated purpose (recall memories) indicate retrieval rather than creation, modification, or deletion.
From the tool's definition Tool name 'memory_similar' and server context indicate a search/retrieval operation (hybrid search with BM25, vectors, recency decay).
Documented attack patterns abuse exactly the kind of access memory_similar gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Rekal, and nothing reaches the server without passing your rules. This is the rule we recommend for memory_similar:
{
"version": "1",
"default": "deny",
"tools": {
"memory_similar": {}
}
}memory_similar is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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memory_similar. It is categorised as a Read tool in the Rekal MCP Server, which means it retrieves data without modifying state.
Register the Rekal MCP server in PolicyLayer and add a rule for memory_similar: 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 Rekal. Nothing to install.
memory_similar 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_similar 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_similar. 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_similar is provided by the Rekal MCP server (janbjorge/rekal). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Rekal, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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21 Rekal tools catalogued and risk-classified — across an index of 43,000+ MCP servers.