daily

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

With no annotations supplied, the description carries the full burden, and it does disclose real behavior: results are oldest-first, zero-usage days are included rather than omitted, and 'local day' defines the bucketing timezone. 'API-equivalent dollars' usefully signals these are computed costs, not billed amounts. It does not state that the operation is read-only or what a day record contains.

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?

A single front-loaded sentence where each clause adds information: metric, granularity, ordering, and gap behavior. No filler, though it lacks an explicit subject/verb, reading more like a caption than a tool instruction.

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?

The tool is simple (one optional integer parameter), and the description covers units, granularity, ordering, and empty-day handling. However, with no output schema and no annotations, it should also say roughly what each daily entry contains and that 'days' controls the window, both of which are left to the schema or to guesswork.

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 0% for the single 'days' parameter, and the description never mentions it, so the caller learns nothing about the lookback window or its default from the prose. The phrase 'per local day' gives indirect context for how the window is bucketed, which keeps this from being a 2.

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 names the metric set (tokens and API-equivalent dollars), the granularity (per local day), and the ordering, which effectively tells an agent this is a daily time-series read. It is clear enough to distinguish from an aggregate like usage_summary, though it never states a verb ('returns'/'lists') or explicitly names a sibling it is not.

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?

There is no when-to-use guidance and no reference to any of the five siblings (usage_summary, plan_limits, quota_forensics, sessions, budget_status). An agent must infer that this is the per-day breakdown versus a summary tool purely from the phrase 'per local day'.

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