hippo_fact_supersede
Cycle #78 (2026-05-16). Declare old_id as superseded
This record as markdown: /tools/verimem/hippo-fact-supersede.md
What hippo_fact_supersede does on Verimem
AI agents use hippo_fact_supersede to create or update resources in Verimem, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Verimem environment.
Why hippo_fact_supersede is rated Medium
This tool modifies the state of an existing memory/fact record by declaring it superseded, which is a metadata update (Write). It does not irreversibly delete data — bi-temporal systems typically retain the old record with a superseded status, making this reversible. However, it does alter the authoritative status of a fact, which could mislead an AI agent if misused.
From the tool's definition Declare `old_id` as superseded — marks an existing fact record as superseded/replaced
Attacks that exploit this kind of access
The rule that runs hippo_fact_supersede safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Verimem, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For hippo_fact_supersede, this is the rule to start with:
hippo_fact_supersede stays usable, but capped: an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Verimem, apply this rule, and every hippo_fact_supersede call is checked against it from then on.
Questions about hippo_fact_supersede
Cycle #78 (2026-05-16). Declare old_id as superseded. It is categorised as a Write tool in the Verimem MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Verimem MCP server in PolicyLayer and add a rule for hippo_fact_supersede: 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 Verimem. Nothing to install.
hippo_fact_supersede is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the hippo_fact_supersede 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 hippo_fact_supersede. 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.
hippo_fact_supersede is provided by the Verimem MCP server (aureliocpr-ctrl/verimem). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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