hash_increment

Increment field value in hash. Args: key: The name of the key field: The field name amount: Amount to increment by (default: 1) Returns: New value or error message

SERVERAWS SOURCE@awslabs/mcp

Medium RISK CLASS

Category Write

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity verified Pull the record →

This record as markdown: /tools/aws/hash-increment.md

WHAT IT DOES

What hash_increment does on AWS

AI agents use hash_increment to create or update resources in AWS, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your AWS environment.

RISK

Why hash_increment is rated Medium

This tool modifies an existing value in a hash data structure by incrementing it. This is a write operation (reversible modification) — the field value is updated but not permanently destroyed. Misuse could corrupt data or cause unintended numeric drift in stored values, warranting medium severity.

From the tool's definition Increment field value in hash

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs hash_increment safely

PolicyLayer is an MCP gateway: it sits between your AI agents and AWS, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For hash_increment, this is the rule to start with:

hash_increment Rate-limited

hash_increment 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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "hash_increment": {
      "limits": [
        {
          "counter": "hash_increment_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect AWS, apply this rule, and every hash_increment call is checked against it from then on.

FAQ

Questions about hash_increment

What does the hash_increment tool do? +

Increment field value in hash. Args: key: The name of the key field: The field name amount: Amount to increment by (default: 1) Returns: New value or error message. It is categorised as a Write tool in the AWS MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on hash_increment? +

Register the AWS MCP server in PolicyLayer and add a rule for hash_increment: 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 AWS. Nothing to install.

What risk level is hash_increment? +

hash_increment is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit hash_increment? +

Yes. Add a rate_limit block to the hash_increment 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.

How do I block hash_increment completely? +

Set action: deny in the PolicyLayer policy for hash_increment. 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.

What MCP server provides hash_increment? +

hash_increment is provided by the AWS MCP server (@awslabs/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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