AI agents use create_custom_field_option to create or update resources in Mycase — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Mycase environment.
This tool creates a new option entry in a custom field list, which modifies the law firm's case/client management system configuration. The action is reversible (options can be edited or removed), so it falls under Write rather than Destructive.
From the tool's definition Tool name 'create_custom_field_option' and description 'Add an option to a list-type custom field' indicate creation of new field configuration data.
Attacks that exploit this kind of access
Add an option to a list-type custom field. It is categorised as a Write tool in the Mycase MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Mycase MCP server in PolicyLayer and add a rule for create_custom_field_option: 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 Mycase. Nothing to install.
create_custom_field_option is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the create_custom_field_option 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 create_custom_field_option. 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.
create_custom_field_option is provided by the Mycase MCP server (rosenadvertising/mycase-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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