snow_describe_field
Describe one field on one table, resolved through table inheritance. Walks sys_db_object.super_class to the root class, so fields declared on a parent are found (incident.short_description is declared on task, incident.state on task, cmdb_ci_win_server.name on cmdb_ci). Applies the sys_dictionary...
This record as markdown: /tools/serac/snow-describe-field.md
What snow_describe_field does on Serac
AI agents call snow_describe_field to retrieve information from Serac without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Why snow_describe_field is rated Low
Retrieves and queries field metadata from ServiceNow tables with no side effects.
From the tool's definition Describe one field, returns column_label, internal_type, max_length, mandatory, read_only.
Risk signalsAdmin/system-level operation
Attacks that exploit this kind of access
The rule that runs snow_describe_field safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Serac, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For snow_describe_field, this is the rule to start with:
snow_describe_field 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 Serac, apply this rule, and every snow_describe_field call is checked against it from then on.
Questions about snow_describe_field
Describe one field on one table, resolved through table inheritance. Walks sys_db_object.super_class to the root class, so fields declared on a parent are found (incident.short_description is declared on task, incident.state on task, cmdb_ci_win_server.name on cmdb_ci). Applies the sys_dictionary_override rows found anywhere on that chain, nearest table wins. Returns: the declaring table, the full parent-class chain, the effective column_label / internal_type / max_length / mandatory / read_only / default_value / reference target / reference qualifier / attributes after overrides, the raw dictionary row and the override rows it merged, and the field. It is categorised as a Read tool in the Serac MCP Server, which means it retrieves data without modifying state.
Register the Serac MCP server in PolicyLayer and add a rule for snow_describe_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 Serac. Nothing to install.
snow_describe_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 snow_describe_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 snow_describe_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.
snow_describe_field is provided by the Serac MCP server (serac-labs/serac). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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