AI agents use hash_set to create or update resources in Awslabs Amazon Sns Sqs — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Awslabs Amazon Sns Sqs environment.
This tool modifies data in a hash structure, making it a Write operation. While the exact scope of what 'hash' refers to in the SNS/SQS context is unclear from the minimal description, setting a field is typically a reversible operation. Severity is medium because unintended modifications could affect message metadata or configuration in a recoverable way.
From the tool's definition "Set field in hash" indicates modification of data structure (hash/dictionary). The action is reversible (fields can be updated or cleared) and does not irreversibly delete data or execute arbitrary code.
Documented attack patterns abuse exactly the kind of access hash_set gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Awslabs Amazon Sns Sqs, and nothing reaches the server without passing your rules. This is the rule we recommend for hash_set:
{
"version": "1",
"default": "deny",
"tools": {
"hash_set": {
"limits": [
{
"counter": "hash_set_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}hash_set 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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Set field in hash. It is categorised as a Write tool in the Awslabs Amazon Sns Sqs MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Awslabs Amazon Sns Sqs MCP server in PolicyLayer and add a rule for hash_set: 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 Awslabs Amazon Sns Sqs. Nothing to install.
hash_set 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 hash_set 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 hash_set. 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.
hash_set is provided by the Awslabs Amazon Sns Sqs MCP server (awslabs.amazon-sns-sqs-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Awslabs Amazon Sns Sqs, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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