AI agents call get_fields to retrieve information from Struct without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves structural information (field definitions) from a data structure. It performs a query operation that returns data without modifying, deleting, or executing code. The operation is read-only with no destructive or side effects, making it a straightforward Read category tool with low severity.
From the tool's definition Tool name 'get_fields' and description 'Get all fields for a structure' indicate retrieval of metadata without modification or side effects.
Attacks that exploit this kind of access
Get all fields for a structure. It is categorised as a Read tool in the Struct MCP Server, which means it retrieves data without modifying state.
Register the Struct MCP server in PolicyLayer and add a rule for get_fields: 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 Struct. Nothing to install.
get_fields 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 get_fields 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 get_fields. 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.
get_fields is provided by the Struct MCP server (laurears/struct-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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