Update typed/meta fields of NPC mnemons (visibility, tags, npcType, faction membership, etc.). Does NOT modify content blocks — use update_mnemons_content for that. Set visibility=PUBLIC on multiple NPCs in a single call by listing them in items[].
Risk signalsHigh parameter count (12 properties)
Part of the Argo Mcp server.
Free to start. No card required.
AI agents use update_npc_mnemons to create or modify resources in Argo Mcp. Write operations carry medium risk because an autonomous agent could trigger bulk unintended modifications. Rate limits prevent a single agent session from making hundreds of changes in rapid succession. Argument validation ensures the agent passes expected values.
Without a policy, an AI agent could call update_npc_mnemons repeatedly, creating or modifying resources faster than any human could review. PolicyLayer's rate limiting ensures write operations happen at a controlled pace, and argument validation catches malformed or unexpected inputs before they reach Argo Mcp.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
{
"version": "1",
"default": "deny",
"tools": {
"update_npc_mnemons": {
"limits": [
{
"counter": "update_npc_mnemons_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}See the full Argo Mcp policy for all 61 tools.
These attack patterns abuse exactly the kind of access update_npc_mnemons gives an agent. Each links to the full case and the policy that stops it:
Other write tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.
Update typed/meta fields of NPC mnemons (visibility, tags, npcType, faction membership, etc.). Does NOT modify content blocks — use update_mnemons_content for that. Set visibility=PUBLIC on multiple NPCs in a single call by listing them in items[].. It is categorised as a Write tool in the Argo Mcp MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Argo MCP server in PolicyLayer and add a rule for update_npc_mnemons: 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 Argo Mcp. Nothing to install.
update_npc_mnemons 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 update_npc_mnemons 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 update_npc_mnemons. 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.
update_npc_mnemons is provided by the Argo MCP server (argo-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 61 Argo Mcp tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
4,600+ MCP servers and 31,000+ tools scanned and risk-classified.