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

Annotations already declare readOnlyHint=false, destructiveHint=true, and openWorldHint=true, so the agent knows this is a destructive write. The description adds the meaningful existing-only constraint, but says nothing about the confirm-token preview flow, reversibility, or what a successful write returns.

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?

Two compact clauses, front-loaded with the verb+resource and immediately followed by the scope restriction. Nothing is wasted, though it is arguably too terse given the mutation's complexity.

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?

For a destructive mutation with a nested, undocumented 'patches' parameter and no output schema, the description leaves real gaps. account_id and confirm_id are covered by schema descriptions, but the agent gets no meaningful picture of what it can actually change or how confirmation works.

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 only 50%, and the two undocumented parameters are the important ones: 'patches' (an untyped nested object) and 'ad_group_id'. The description partially compensates by hinting patches accepts status (ENABLED|PAUSED), but leaves the rest of the patch structure opaque.

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?

The description names a specific verb (Aggiorna) and resource (ad group Sponsored Brands), and adds a scope qualifier (ESISTENTE) plus an explicit negative (NON crea ad group nuovi) that separates it from the create siblings. It is clear what the tool does, though it does not name a specific alternative tool the way the strongest examples do.

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?

It implies usage ('update an EXISTING ad group') and rules out creation, which is useful. But there is no explicit when-to-use guidance beyond that negative, and the critical two-step preview/confirm workflow is not surfaced in the description at all.

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