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

Annotations already declare write/openWorld/destructive/non-idempotent, and the description adds substantial context the annotations cannot convey: the error returned when multiple accounts exist, the error when no account is connected (with a URL), and the constraint that each brand pins to exactly one customerId. It does not mention irreversibility or permissions beyond the connection requirement, so 4 rather than 5.

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?

Front-loaded with the core action, then structured into two labeled cases plus a follow-up chain. The bullets earn their place by encoding distinct decision paths, though the prompt text is a bit long.

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?

No output schema exists, but the description covers error behavior, prerequisite (connected Google Ads account), and post-creation workflow. It omits what the created brand returns (e.g., an ID), which is minor for a create tool.

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 coverage is 100%, so the baseline is 3; the description earns more by explaining the conditional requirement logic for customerId (required for multi-account users, safe to omit only with a single account) and the downstream discovery flow, which the schema alone does not state.

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+resource ('Register a new brand') and names the account scope, clearly distinguishing it from sibling list_brands and set_brand_ad_account. An agent immediately knows this creates a brand entity bound to a Google Ads customerId.

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 prescribes when to pass customerId versus omit it, tells the agent to call list_ad_accounts first and surface the results to the user, and specifies the follow-up chain (fetch_homepage_content then update_value_prop_doc). Nothing is left to inference.

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