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

With no annotations, the description carries the full burden and does disclose meaningful traits: 'no row limit' and 'Partners see own partner scope only' (a data-scoping/auth constraint). It also states the aggregation granularity (by carrier and user). It stops short of describing the exact return structure or any rate/format limits, so not a 5.

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 tight sentences, front-loaded with the PREFERRED marker and the core purpose, followed by return shape and the sibling alternative. No filler; every sentence earns its place.

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 5-optional-param aggregation tool with no output schema and no annotations, the description covers purpose, output granularity, scope restriction, and the alternative. The defaults (today UTC, same-as-dateFrom) live in the schema, but the return format detail is thin, keeping it just short of complete.

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 the schema already documents all five optional parameters with types, defaults, and formats. The description only implies date and carrier usage via its example ('how many DHL labels today') and adds no syntax 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?

States a specific verb+resource (SummarizeUsageRecords) and clarifies the output shape: aggregated counts by carrier and user. It explicitly contrasts with a sibling (SearchUsageRecords rows), so an agent can distinguish it without opening any 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?

Marks itself PREFERRED for counts and totals, gives a concrete example (how many DHL labels today), and names the alternative to avoid (fetching hundreds of SearchUsageRecords rows). When-to-use and when-not-to-use are both explicit.

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