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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds genuinely non-structured context: the data is near-real-time, the used/remaining budget values are estimates rather than finalized cost, and omitting ad_product still defaults to SP. These behavioral caveats exceed what the annotations convey.

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?

Three sentences, front-loaded with the 'Use for' trigger, followed by the default-reset clarification and the estimation caveat. No filler or redundant restatement of the title.

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 15-parameter tool with an output schema and full schema coverage, the description supplies the interpretive context an agent needs (near-real-time estimates, SP default, finalized-spend routing). Nothing critical is missing, though it could note the date-range/pagination behavior at a higher level.

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 schema already documents all 15 parameters including defaults and ranges. The description only reinforces the ad_product default (SP), adding marginal meaning beyond the schema. Baseline 3 is appropriate.

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 ('budget usage and pacing snapshots') and names the exact scope it covers (SP, SB, SD) plus the derived fields produced (usage percentage, estimated used and remaining budget by campaign). An agent can distinguish it from finalized-spend siblings like get_campaign_performance without opening the schema.

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 opens with an explicit use case ('Use for SP, SB, or SD budget usage and pacing snapshots') and adds a negative directive routing finalized spend to 'retained campaign performance.' Clear context and an exclusion are present, though the sibling tool is named descriptively rather than by exact tool name.

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