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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds genuinely non-obvious behavior: RM logs a session only at LOGOUT, so today's hours understate concurrency while completed days are accurate. That caveat — plus the per-day-peak vs hourly-profile return shape and the org-wide scoping constraint — is exactly the kind of context structured fields cannot carry.

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 purpose, then a scannable bulleted example block, then returns, then the caveat, then the args. Length is justified by the amount of genuinely useful information; every sentence contributes routing or invocation value with no filler.

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?

Although an output schema exists (so return values need not be explained), the description still summarizes the key outputs, then covers scope, the today-incompleteness caveat, and both argument formats/defaults. For a zero-required-param, zero-coverage-schema analysis tool, nothing an agent needs to call it correctly is missing.

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 must compensate and it does: both parameters are documented with their MM/DD/YYYY format and their defaults (start_date = 6 days ago / 7-day window, end_date = today). No ambiguity remains about how to supply the arguments.

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 opening sentence names a specific verb and resource ('Rent Manager user login activity and concurrent-user counts') and even cites the underlying source (UserLog, 3). It also declares the scope boundary ('Org-wide by nature — there is no property scope'), which sharply separates it from property-scoped analyses like analyze_occupancy_trend or analyze_rent_roll in the sibling set.

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?

Four concrete example user questions ('How many users were logged in at one time yesterday?', 'peak concurrent user count this week', 'failed login attempts') give an agent strong routing signal for when to pick this tool. It does not, however, name an alternative sibling or an explicit when-not condition, so it falls just short of the 5 bar.

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