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

Annotations only declare readOnlyHint, so the description carries most of the burden and does well: it discloses the comparative baseline (usual day at this same hour), the breadth of the report (people, new people, behavior, spikes, slow stretches, sales/money, live ads, causes), and that a past `date` returns a whole-day view rather than an as-of-now view. Cost, latency, and freshness limits are not mentioned.

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 the use case, then the substance, then the two parameter rules — a sensible order. It's a single dense paragraph with minor redundancy against the schema (

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?

With an output schema present this doesn't need to describe return structure, and annotations already cover the read-only safety profile, so the remaining need is use-context and parameter scoping — both supplied. The gap is family-level: for a 7-tool sibling set with an adjacent 'why' tool, the description should say when this one beats the others.

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 both parameters are already documented and the description's restatement of 'leave out app for every app together' and the date example adds little. The one genuine addition is that `date` renders that day the same way, clarifying the semantics of the past-day mode. Baseline 3 applies.

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 specifies a concrete deliverable: a current-day snapshot comparing people so far against a usual day at the same hour, plus new people, spikes, sales, ads, and drivers. That's far more than a restatement of the name. It stops short of 5 because the 'why today is busier or quieter' clause overlaps with the sibling why_did_it_change and the description never draws that line.

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 gives an explicit trigger phrase ('how is it going right now / today') and explicitly tells the agent how to widen scope by omitting `app` and how to re-point at a past day with `date`. What's missing is any exclusion or named alternative — an agent deciding between this, why_did_it_change, and timeline gets no routing rule.

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