AdCopilot

GA4: create custom dimension

ga4_create_custom_dimension

Create a custom dimension on a GA4 property. It adds one custom dimension and changes nothing existing; reports show it from now on, for events that send the parameter it names.

Tools revision: d80f65c0.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "property": "<property>",
      "parameter_name": "<parameter_name>",
      "display_name": "<display_name>"
    },
    "name": "ga4_create_custom_dimension"
  }
}

Input Schema

Name	Required	Default
`scope`	No	EVENT
`property`	Yes
`display_name`	Yes
`parameter_name`	Yes

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 23, 2026

TDQS

B3.4/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false), and the description adds genuinely new behavioral context: it creates exactly one dimension, mutates nothing existing, and takes effect in reporting going forward only for events that send the named parameter. It omits that re-invocation is not idempotent (duplicate/conflicting names) and says nothing about GA4's per-property dimension caps.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two tight sentences lead with the action and immediately follow with its side effects; nothing is buried. The trailing "Tools revision: d80f65c0." is internal bookkeeping that earns no place in an agent-facing definition.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return values need no explanation, and the effect-on-reporting behavior is well covered. However, for a creation tool with a 0%-documented schema, the missing scope semantics and any note on naming constraints or dimension limits leave a real gap an agent would hit on first use.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters2/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0% across four parameters, so the description must carry the load and largely does not. It references the property and the parameter name obliquely, but never explains display_name, and critically never explains scope (default EVENT) or the EVENT vs USER vs ITEM distinction, which is the single most consequential choice in this call.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb and resource ("Create a custom dimension on a GA4 property"), which an agent can distinguish from ga4_create_custom_metric and ga4_update_custom_dimension by the noun alone. It stops short of naming those siblings explicitly, so the differentiation is inferred rather than stated.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

"It adds one custom dimension and changes nothing existing" implicitly separates this from the update tool and signals it is for new dimensions only. There is no explicit when-not guidance, no prerequisite (e.g. dimension limits, admin access), and no pointer to ga4_list_custom_dimensions to check for existing names.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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