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

Goes well beyond the readOnly/idempotent annotations: response is cached for 5 minutes, the 1-year/3-month window limits, the account-registered region always overrides the region argument (region is fixed per account, no mixing), and a wrong-region call yields 401. These are exactly the operational constraints an agent needs before invoking.

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?

Front-loaded with purpose, then returns, then exclusions, then constraints — a sensible ordering with no filler sentences. It is dense and information-heavy for one paragraph, but nearly every clause carries operational value; the region explanation is somewhat redundant with the schema text.

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?

No output schema exists, and the description compensates by describing the return shape (period totals plus a daily_data[] time series with named fields and units). Combined with the limits, caching, and region precedence notes, nothing needed to call this correctly is missing.

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 baseline is 3, but the description adds meaning the schema does not convey: region is fixed per account and the account-level region silently overrides the passed argument, and the period arguments must be split when exceeding 3 months. The region resolution pointer to kollus://guidance/regions is repeated from the schema but the precedence rule is genuinely new.

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?

Specific verb+resource (daily statistics summary) with the exact endpoint stated, and it enumerates the returned metric families (transfer, traffic, storage, transcoding, visitor) with units. It explicitly excludes play-count/watch-time fields and names the sibling get_statistics_content_rank for those, so the agent can distinguish it from siblings without opening a 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?

Gives concrete when-to-use rules: date range must be within the last year, max 3 months per call with long ranges split into 3-month chunks, and play-count requests must be routed to get_statistics_content_rank. It also states that group_by-style distributions (device/region/cdn) are unsupported by the REST API, preventing a wasted attempt.

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