Add a value to the cache only if the key doesn't exist.
AI agents use cache_add to create or update resources in Amazon EKS MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Amazon EKS MCP Server environment.
This tool creates or modifies cache entries, which is a Write operation (not Read, as it has side effects; not Execute, as it doesn't run code or trigger external operations; not Destructive, as cache values can be updated or cleared).
From the tool's definition Tool name 'cache_add' and description 'Add a value to the cache' indicates a create/write operation that modifies cache state. The conditional 'only if the key doesn't exist' shows it prevents overwriting, making it a reversible write operation.
Documented attack patterns abuse exactly the kind of access cache_add gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Amazon EKS MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for cache_add:
{
"version": "1",
"default": "deny",
"tools": {
"cache_add": {
"limits": [
{
"counter": "cache_add_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}cache_add 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.
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Add a value to the cache only if the key doesn't exist. It is categorised as a Write tool in the Amazon EKS MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Amazon EKS MCP Server MCP server in PolicyLayer and add a rule for cache_add: 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 Amazon EKS MCP Server. Nothing to install.
cache_add 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 cache_add 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 cache_add. 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.
cache_add is provided by the Amazon EKS MCP Server MCP server (awslabs.eks-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Amazon EKS MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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805 Amazon EKS MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.