update_custom_field

THE RISK

Medium Risk

Why update_custom_field needs a policy

This tool modifies existing CRM data (custom fields) in a reversible manner. It falls under Write category as it creates or modifies data reversibly. Severity is medium because misuse could corrupt or modify critical business data in the CRM system, but the blast radius is limited to custom field definitions rather than bulk contact or financial data.

From the tool's definition Tool name 'update_custom_field' and description 'Update an existing custom field' indicate modification of data. The action is reversible (fields can be updated again or reverted), not destructive or financial.

Documented attack patterns abuse exactly the kind of access update_custom_field gives an agent:

POLICY

How to control update_custom_field

PolicyLayer is an MCP gateway — it sits between your AI agents and GoHighLevel MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for update_custom_field:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "update_custom_field": {
      "limits": [
        {
          "counter": "update_custom_field_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

update_custom_field stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

Create a free account and register GoHighLevel MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

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All 64 GoHighLevel MCP Server tools →

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Go deeper

Govern customer-ops agents → PII redaction, approval on external messages, and no-bulk-delete rules on the records agents change.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →
PolicyLayer vs alternatives → How deterministic, per-call MCP policy compares with gateways, identity layers, and authorisation platforms.

FAQ

Questions about update_custom_field

What does the update_custom_field tool do? +

Update an existing custom field. It is categorised as a Write tool in the GoHighLevel MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on update_custom_field? +

Register the GoHighLevel MCP Server MCP server in PolicyLayer and add a rule for update_custom_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 GoHighLevel MCP Server. Nothing to install.

What risk level is update_custom_field? +

update_custom_field is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit update_custom_field? +

Yes. Add a rate_limit block to the update_custom_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.

How do I block update_custom_field completely? +

Set action: deny in the PolicyLayer policy for update_custom_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.

What MCP server provides update_custom_field? +

update_custom_field is provided by the GoHighLevel MCP Server MCP server (basicmachines-co/open-ghl-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every GoHighLevel MCP Server tool call.

Start from GoHighLevel MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →