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

Annotations already establish readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral detail beyond annotations: the exact threshold calculation, default threshold of 90%, and the conditional enrichment from Amazon's live budgetUsagePercent snapshot '(when available)'.

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 sentences with no filler: the first states the purpose and selection rule, the second explains the enrichment and points to the full-history alternative. The most important information is front-loaded.

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 read-only tool with all parameters optional and output schema absent, the description conveys the core invocation semantics, default threshold, enrichment field, and where to get detailed history. Minor ambiguity remains around how start_date/end_date interact with period_days and average daily spend, but the defaults and optionality make successful invocation likely.

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 60%; the description clarifies threshold semantics ('default 90%') but not start_date/end_date semantics. threshold_pct gets useful meaning from the description, while period_days and profile_id are already covered in the schema. The uncompensated date parameters keep this at a mid score.

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?

Description opens with a precise verb and resource: 'Find campaigns approaching or exceeding their daily budget.' It also specifies the selection rule (average daily spend >= threshold) and the enrichment field, making the tool's purpose unmistakable and distinct from generic campaign-list or search siblings.

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?

The description gives clear when-to-use context: budget alerts based on utilization threshold. It also points to an alternative for fuller data ('Full per-day usage history: ppc_query dataset budget_usage'), which helps an agent choose between snapshot alerts and detailed history, though it stops short of explicit exclusion wording.

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