json_set

A write tool on the AWS MCP server.

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/json-set.md

WHAT IT DOES

What json_set does on AWS

AI agents use json_set 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 json_set is rated Medium

The name 'json_set' implies a write operation that creates or modifies JSON data. However, with no description available, the exact behavior is unknown. Based on naming conventions, 'set' operations typically modify or create data reversibly, placing this in the Write category. Confidence is low due to the absence of a description.

From the tool's definition Tool name 'json_set' suggests setting/writing JSON data, but description is empty and uninformative.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs json_set 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 json_set, this is the rule to start with:

json_set Rate-limited

json_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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "json_set": {
      "limits": [
        {
          "counter": "json_set_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 json_set call is checked against it from then on.

FAQ

Questions about json_set

What does the json_set tool do? +

json_set is a write tool on the AWS MCP server. 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 json_set? +

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

What risk level is json_set? +

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

Can I rate-limit json_set? +

Yes. Add a rate_limit block to the json_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.

How do I block json_set completely? +

Set action: deny in the PolicyLayer policy for json_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.

What MCP server provides json_set? +

json_set 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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