set_custom_field_values

Set or clear custom field values for a CRM entity. Values are stored as strings; pass null to clear a value.

SERVERFavCRM SOURCEhttps://api.favcrm.io/mcp

Medium RISK CLASS

Category Write

Parameters 33 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/io-favcrm-favcrm/set-custom-field-values.md

WHAT IT DOES

What set_custom_field_values does on FavCRM

AI agents use set_custom_field_values to create or update resources in FavCRM, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your FavCRM environment.

Parameter	Type	Required	Description
`values`	array	Yes	Values to upsert
`entityId`	string	Yes	Entity ID
`entityType`	string	Yes	Entity type

Parameters from the server's own tool schema.

RISK

Why set_custom_field_values is rated Medium

This tool modifies CRM entity data (custom field values) but the changes are reversible—values can be updated or cleared without permanent deletion. This fits the Write category.

From the tool's definition Tool description states "Set or clear custom field values for a CRM entity," explicitly performing create/modify operations on CRM data that are reversible (values can be cleared by passing null).

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs set_custom_field_values safely

PolicyLayer is an MCP gateway: it sits between your AI agents and FavCRM, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For set_custom_field_values, this is the rule to start with:

set_custom_field_values Rate-limited

set_custom_field_values 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.

View as policy code

policy.json

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

LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect FavCRM, apply this rule, and every set_custom_field_values call is checked against it from then on.

FAQ

Questions about set_custom_field_values

What does the set_custom_field_values tool do? +

Set or clear custom field values for a CRM entity. Values are stored as strings; pass null to clear a value. It is categorised as a Write tool in the FavCRM MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

What parameters does set_custom_field_values accept? +

set_custom_field_values accepts 3 parameters: values, entityId, entityType. Required: values, entityId, entityType. The full parameter table on this page comes from the server's own tool schema.

How do I enforce a policy on set_custom_field_values? +

Register the FavCRM MCP server in PolicyLayer and add a rule for set_custom_field_values: 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 FavCRM. Nothing to install.

What risk level is set_custom_field_values? +

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

Can I rate-limit set_custom_field_values? +

Yes. Add a rate_limit block to the set_custom_field_values 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 set_custom_field_values completely? +

Set action: deny in the PolicyLayer policy for set_custom_field_values. 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 set_custom_field_values? +

set_custom_field_values is provided by the FavCRM MCP server (https://api.favcrm.io/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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