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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds nothing beyond that — no note on pagination, result size, or what happens for a property with no custom metrics; the revision string carries no behavioral meaning.

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

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

The core sentence is short and front-loaded with the verb and resource. The trailing 'Tools revision: d80f65c0.' is internal metadata that consumes space without helping an agent decide or invoke.

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

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 not be explained, and the annotations cover the read-only/idempotent profile. For a one-parameter tool the definition is close to sufficient, but the missing property identifier format is a real invocation blocker.

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

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

Schema description coverage is 0%, so the single 'property' parameter is undocumented in both schema and description. GA4 property identifiers have a specific form ('properties/123456789' vs. a bare numeric ID) that an agent cannot infer, and the description does not supply it.

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

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

States a specific verb ('List') and resource ('custom metrics') scoped to 'a GA4 property', which distinguishes it from ga4_create_custom_metric and ga4_update_custom_metric. It does not explicitly contrast with the adjacent ga4_list_custom_dimensions, but the resource noun is unambiguous.

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

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

There is no guidance on when to call this versus the create/update/list-dimensions siblings, and no stated prerequisites such as needing an existing property or when a listing is preferable to a report. Usage must be inferred entirely from the tool name.

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