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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so the safety profile is covered. The description adds useful behavioral context: account/optional-campaign scoping and the hook-based comparison workflow when multiple draft_ad_variants campaigns exist.

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 opening sentence and usage guidance are tight and front-loaded. The routing sentence is compressed to the point of being slightly cryptic, but it still earns its place by giving actionable post-retrieval guidance.

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 simple read-only tool with fully described parameters, the description covers the core use cases and routing behavior. It does not enumerate the exact return fields or pagination, but 'spent' and 'returned' give enough orientation given the lack of an output schema.

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%, so the baseline is 3. The description's 'account (and optional campaign)' wording echoes the schema but adds no new semantic detail beyond what the parameter descriptions already provide.

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 states a specific verb and resource ('Get X ads results for an account') and immediately distinguishes itself from get_ads_performance (Meta). An agent can clearly tell this tool is for X/Twitter ads, not Meta ads.

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 explicitly says when to use the tool ('when the user asks how their X ads are doing, what they spent, or what it returned') and names the alternative tool for Meta. The routing note also gives concrete guidance on comparing hook-tagged campaigns.

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