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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds useful resource-type context ('SharedSets of type BRANDS') and the fact that it returns a total alongside per-list rows, but return-shape detail is largely redundant given an output schema exists.

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 purpose and the reuse-vs-duplicate rationale are front-loaded in two tight sentences. The trailing Google Ads API documentation link is boilerplate that does not help tool selection, keeping this from a 5.

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?

With annotations covering the safety profile and an output schema covering return values, the description supplies what is needed: scope, resource type, and the reuse workflow. It omits any note on result limits or pagination, which is a minor gap for a 'list all' tool on an account that may hold many shared sets.

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 100% and the single customer_id parameter is fully documented in the schema, including its default behavior. The description adds no syntax, format, or defaulting information beyond the schema, so the baseline 3 applies.

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 and resource ('List all brand lists') and disambiguates the resource by naming its underlying type ('SharedSets of type BRANDS'), which no sibling tool does. It also names the sibling tools it relates to (add_to_brand_list, propose_brand_list), so an agent can distinguish it from get_brand_list_brands and get_brand_list_campaigns without opening a schema.

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?

Explicitly frames the tool as the lookup step before reusing a list with add_to_brand_list rather than duplicating it with propose_brand_list, which gives clear routing guidance to alternatives. It stops short of stating exclusions (e.g., use get_brand_list_brands when you need the members themselves), so it is clear context rather than full when/when-not coverage.

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