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

The annotations already declare this as a safe, read-only, closed-world operation. The description adds the report's contents and lookback period, but it does not clarify important behavioral details such as timezone, how signups are counted, or whether the change is absolute or percentage-based.

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?

The definition is a single front-loaded sentence listing the report metrics and default period. There is no redundant or filler wording.

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 simple read-only report with one optional parameter and no output schema, the description is largely sufficient: it states what is returned and the default lookback. Remaining gaps are the unspecified timezone/change calculation and the lack of routing guidance versus sibling signup tools.

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?

The schema has no parameter descriptions, but the description explains that the days parameter controls the lookback window and defaults to 7. It does not mention the schema's 1-365 bounds or clarify whether the window uses calendar days.

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 clearly identifies a growth report by stating the exact metrics returned: signups per day, total, today's count, and change versus the previous period. It does not differentiate this report from nearby siblings such as get_recent_signups or get_activation_rate, so sibling selection remains slightly ambiguous.

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 explicit guidance on when to use this tool instead of alternatives like get_recent_signups, get_active_users, or get_retention. The default 7-day period is stated, but that is a parameter default rather than usage guidance.

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