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

The annotations already establish that this is a safe, non-destructive, closed-world read, so the description doesn't need to repeat that. It does add genuinely useful behavior beyond the annotations, namely the 7-day default window and the join-date sort order, but it is silent on what 'active' actually means and on result volume beyond the default severity.

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 with no padding, and the filtering rule precedes the ordering rule. It is efficient, though the elliptical phrasing 'last N days' relies on the parameter name to be fully unambiguous.

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?

This is a simple two-parameter read with no output schema, and the description covers the window and ordering, so the basics are there. It falls short on defining the activity criterion and on the limit parameter, which matters because nothing else in the structured data explains them.

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%, so the description bears the full burden. It clarifies only the days parameter and only restates the default already encoded in the schema; the limit parameter (default 20, max 50, and whether it is a page size or a cap) is never mentioned.

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 states a specific resource and filter: users active within the last N days, with a default window and an explicit ordering (most recently joined first). This is far more informative than the bare name, but it never distinguishes the tool from close siblings such as get_user_activity, get_recent_signups, or list_users.

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?

Usage is only implied: an agent can infer this is the tool for 'who was recently active' as opposed to find_inactive_accounts, but no when-to-use or when-not-to-use rule is stated, and no sibling is named as an alternative.

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