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

Annotations cover only safety (readOnly, non-destructive). The description adds genuinely non-obvious behavior: the billable amount is computed as hours times the rate each entry was logged with, mixed currencies are summed as plain numbers, own projects roll up everyone's time and money while shared projects expose only the user's own hours and no amounts. These are exactly the semantics an agent needs to interpret results correctly.

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 what gets computed, then the grouping dimensions, then output units, then the caveats. Two dense sentences with virtually no filler, though the long parenthetical about rates and currency does slow the read slightly.

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 carries the return-shape burden and does so well by naming the three output fields and the currency edge case. Remaining gaps are minor: no mention of row limits, pagination, or empty-date-range behavior for a seven-parameter report.

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 the schema already documents all seven parameters and their defaults. The description restates the `by` enum values ('project, client, person, task or day') without adding format or constraint 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 precise verb (adds up) and resource (time logged in a date range) plus the exact aggregation dimensions and output fields (minutes, billable minutes, billable amount in cents). An agent can distinguish this aggregated report from list_time_entries or get_week_timesheet without opening a schema.

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 implied rather than stated: the aggregation output makes clear this is an analytics/reporting call, and the note about which projects count whose time is useful scoping context. But it never names alternatives such as export_time_report, get_week_timesheet or get_billing_report, nor the conditions that would select one over the other.

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