json_strlen
Get the length of string at path. Args: key: The name of the key path: The path in the JSON document Returns: String length or error message
This record as markdown: /tools/aws/json-strlen.md
What json_strlen does on AWS
AI agents call json_strlen to retrieve information from AWS without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Why json_strlen is rated Low
The json_strlen tool retrieves metadata (string length) from a JSON document without modifying, deleting, or executing any operations. It is purely informational and poses minimal risk of misuse by an AI agent.
From the tool's definition Tool description states 'Get the length of string at path' with arguments for key and path, returning 'String length or error message'. This is a query/retrieval operation with no side effects.
Attacks that exploit this kind of access
The rule that runs json_strlen 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_strlen, this is the rule to start with:
json_strlen is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect AWS, apply this rule, and every json_strlen call is checked against it from then on.
Questions about json_strlen
Get the length of string at path. Args: key: The name of the key path: The path in the JSON document Returns: String length or error message. It is categorised as a Read tool in the AWS MCP Server, which means it retrieves data without modifying state.
Register the AWS MCP server in PolicyLayer and add a rule for json_strlen: 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.
json_strlen is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the json_strlen 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 json_strlen. 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.
json_strlen 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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