Vitals by version

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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds genuinely useful behavior beyond that: results are weighted by daily users, ordered newest first, and include the delta versus the previous version — all things an annotations-only view would not reveal.

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 dense sentence with no filler, front-loading the comparison and ordering before the motivation. It is slightly clause-heavy but every clause carries information, so no trimming is obviously warranted.

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 no output schema, the description must convey the shape of results, and it does: per-version metrics, user-weighted, newest first, with change vs previous version. All parameters have defaults and no required inputs, so an agent has everything needed to call it correctly.

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%, with defaults documented for days, metric_sets, and package_name. The description's mention of a 'window' and user weighting adds context but no syntax or format detail beyond the schema, so the 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?

States a specific verb (compares) and resource (vitals across version codes) and specifies the grouping axis plus ordering ('newest first'). This cleanly distinguishes it from sibling per-metric tools like crash_rate and from vitals_summary, which does not segment by version.

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?

Ends with a clear use case — 'to see whether the last release made things worse' — which tells the agent when this tool is the right choice over a single-metric rate tool. It does not, however, explicitly name an alternative or state exclusions, so it stops short of a 5.

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