Get the number of keys in the object at path.
AI agents call json_objlen to retrieve information from Amazon MQ MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The tool performs a read-only introspection of a JSON object to return the count of keys. It has no side effects, does not modify state, and does not execute code or trigger external operations. This is clearly a Read category tool with low severity since misuse would only return incorrect metadata without risk of data loss or compromise.
From the tool's definition Tool description: 'Get the number of keys in the object at path.' This is a simple query operation that retrieves metadata (key count) from an object without modifying, deleting, or executing any operations.
Attacks that exploit this kind of access
Get the number of keys in the object at path. It is categorised as a Read tool in the Amazon MQ MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Amazon MQ MCP Server MCP server in PolicyLayer and add a rule for json_objlen: 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 MQ MCP Server. Nothing to install.
json_objlen 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_objlen 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_objlen. 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_objlen is provided by the Amazon MQ MCP Server MCP server (awslabs.amazon-mq-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.