google-analytics-mcp-server

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ga4 get custom definitions

ga4_get_custom_definitions

Read-onlyIdempotent

Lists custom dimensions and metrics available in GA4 Data API metadata for a property ID, providing a read-only inventory of custom definitions.

Instructions

List custom dimensions and custom metrics exposed by GA4 Data API metadata. Read-only fallback for custom definition inventory.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`propertyId`	Yes	GA4 property ID (numeric, e.g., 123456789)

Output Schema

TableJSON Schema

Name	Required	Description	Default
`result`	Yes	Original tool result: parsed JSON when the text is JSON, otherwise the text or multiple MCP content blocks. Provider fields depend on the selected query.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv2.0.0Sep 30, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": false,
+  "properties": {
+    "result": {
+      "anyOf": [
+        {
+          "additionalProperties": true,
+          "properties": {},
+          "type": "object"
+        },
+        {
+          "items": {},
+          "type": "array"
+        },
+        {
+          "type": "string"
+        },
+        {
+          "type": "number"
+        },
+        {
+          "type": "boolean"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "description": "Original tool result: parsed JSON when the text is JSON, otherwise the text or multiple MCP content blocks. Provider fields depend on the selected query."
+    }
+  },
+  "required": [
+    "result"
+  ],
+  "type": "object"
+}

First observedv1.0.0Aug 29, 2026

TDQS

A3.9/5.0

Behavior3/5

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the safety profile is established. The description adds mild context by clarifying that results come from GA4 Data API metadata and that the tool serves as a fallback, but it does not disclose limitations, pagination, or error behavior beyond what annotations and output schema likely cover.

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

Conciseness5/5

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

Two short sentences with no redundant wording. The core listing behavior is front-loaded, and the fallback qualifier is placed second without detracting from clarity.

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

Completeness5/5

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

This is a low-complexity, one-parameter read-only tool with a rich annotation set and an output schema. The description adequately covers what the tool does and its fallback role; no critical calling information is missing.

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

Parameters3/5

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

Schema description coverage is 100% and the sole parameter propertyId is already fully documented in the schema. The description adds no additional parameter-level meaning, so the baseline score of 3 is appropriate.

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

Purpose5/5

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

The description states a specific verb ('List') and a concrete resource ('custom dimensions and custom metrics exposed by GA4 Data API metadata'). This clearly distinguishes it from broader metadata tools like ga4_get_metadata and from analytics/diagnostic siblings.

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?

The 'Read-only fallback for custom definition inventory' phrase implies a use case but does not explicitly state when to prefer this tool over alternatives such as ga4_get_metadata, nor does it describe when not to use it. Some context is present, but it is not actionable guidance.

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