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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds useful behavioral detail about currency handling (money is never summed across currencies, EUR never added to USD) and hints that billed work is normally excluded. However, the 7-day free-tier clamping — the most consequential runtime behavior — is disclosed only in the schema, not the description.

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?

Two sentences, front-loaded with the core output (hours and billable money) before the grouping options and the fallback. Dense without being padded, though the parenthetical '(group by)' is slightly awkward 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?

For a read-only aggregate with full schema coverage and no output schema, the description covers input intent and the currency model adequately. It does not describe the shape of the returned report (columns/keys per grouping mode) or clarify its relationship to the summary_day/summary_week/summary_client family, which an agent needs in order to pick correctly among 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 100%, so all six parameters are already fully documented, establishing a baseline of 3. The description adds only marginal meaning beyond that: it clarifies that group_by=project yields 'hours per project, how much to bill' and restates the omit-group_by behavior that the schema already specifies.

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 verb and resource — a timesheet report returning total tracked hours and billable money for a period — and enumerates the grouping dimensions (project, day, task, tag). It is clear on its own, but it never distinguishes itself from the summary_day, summary_week, or summary_client siblings that appear to overlap heavily with the day/client grouping modes.

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?

One explicit usage rule is given: 'Omit group_by for the plain total per currency,' which tells the agent how to get the ungrouped variant. Beyond that there is no when-to-use guidance relative to the summary_* siblings, and no note on when to prefer this over export_csv or invoice_summary, so selection among overlapping reporting tools is left to inference.

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