Get detailed explanation of a specific field on a ServiceNow table,
AI agents call explain_field to retrieve information from Now Sdk Ext without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves informational content about ServiceNow table schema—specifically field definitions and explanations. It performs no side effects, creates no data, executes no code, and modifies nothing. It is a straightforward Read operation with minimal risk even if misused by an AI agent, as it only exposes existing field metadata.
From the tool's definition Tool name 'explain_field' and description 'Get detailed explanation of a specific field on a ServiceNow table' indicate retrieval of metadata/documentation about a field with no modification or execution.
Documented attack patterns abuse exactly the kind of access explain_field gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Now Sdk Ext, and nothing reaches the server without passing your rules. This is the rule we recommend for explain_field:
{
"version": "1",
"default": "deny",
"tools": {
"explain_field": {}
}
}explain_field is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get detailed explanation of a specific field on a ServiceNow table,. It is categorised as a Read tool in the Now Sdk Ext MCP Server, which means it retrieves data without modifying state.
Register the Now Sdk Ext MCP server in PolicyLayer and add a rule for explain_field: 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 Now Sdk Ext. Nothing to install.
explain_field 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 explain_field 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 explain_field. 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.
explain_field is provided by the Now Sdk Ext MCP server (sonisoft-cnanda/now-sdk-ext-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Now Sdk Ext, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
86 Now Sdk Ext tools catalogued and risk-classified — across an index of 43,000+ MCP servers.