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

Annotations already declare readOnly=false, destructive=false and non-idempotency, so the safety profile is known. The description adds genuinely useful non-obvious behavior – the needs_confirm gating on spend-raising suggestions – but says nothing about reversibility of an applied change or whether dismissal can be undone. With annotations carrying most of the weight, a 3 fits.

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 short sentences with the core action first and the conditional second; nothing is wasted. The phrasing 'One that raises spend answers needs_confirm first' is a little terse and would read more clearly as a full sentence, but it is front-loaded and efficient.

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 described, and the confirm workflow is covered. However, for a mutating tool that applies settings changes, the description omits whether an applied suggestion is reversible, what happens on a rejected confirm code, and whether approval is atomic – notable gaps for an agent deciding to commit.

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 all three parameters, including the confirm code and its source, are already documented in the schema. The description's mention of needs_confirm only reiterates the schema text rather than adding format or error-handling detail, so the baseline 3 is correct.

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 specific verbs (apply/dismiss) and a specific resource (Siren's suggestions), which clearly separates it from list_ad_suggestions and the campaign-level tools. It stops short of naming any sibling explicitly, so an agent must infer the pairing rather than be told it.

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?

Gives a concrete conditional: suggestions that raise spend require answering needs_confirm first, with set_ad_budget cited as the analogous flow. That covers the main decision point, but there is no guidance on when to dismiss versus apply, or on what to do if the confirm code is missing/invalid.

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