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 ECS MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Amazon ECS MCP Server environment.
This tool creates or modifies cache entries reversibly. It adds a value to a cache with a conditional check (only if key doesn't exist), which is a write operation. The blast radius is low because cache operations are typically non-persistent and reversible, and misuse would only affect cached data, not production systems or data stores.
From the tool's definition Tool name 'cache_add' with description 'Add a value to the cache only if the key doesn't exist' indicates creating or modifying cached data with conditional logic.
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 ECS 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.
Free to start. No card required.
Add a value to the cache only if the key doesn't exist. It is categorised as a Write tool in the Amazon ECS MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Amazon ECS 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 ECS 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 ECS MCP Server MCP server (awslabs.ecs-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Amazon ECS MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
805 Amazon ECS MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.