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

Annotations already declare read-only, idempotent, and non-destructive behavior. The description adds useful aggregation context: grouping by project/day/task/tag, per-currency totals, and the 'how much to bill' framing. It does not mention the free-tier clamping or the unbilled_only default, but those are present in the schema and there is no contradiction.

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 description is two sentences with the core purpose front-loaded and no filler. The parenthetical '(group by)' is slightly redundant, but every clause contributes meaningful information.

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 six-parameter reporting tool with complete schema descriptions and supportive annotations, the definition covers purpose, grouping options, currency behavior, and output formats. It does not fully specify the return structure, but the format enum and per-currency guarantee reduce that gap.

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 six parameters. The description reinforces group_by behavior and adds an illustrative 'hours per project, how much to bill' framing, but it does not substantially extend what the schema already provides.

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 states the resource (timesheet report) and the outputs: total tracked hours, billable money, and how much to bill over a period, with optional grouping. It is distinct from a per-entry list and from invoice_summary by focusing on aggregated billable totals. It does not explicitly name sibling alternatives, so it stops short of a full 5.

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?

The description implies the use case: when you need totals or billable amounts for a period, use this tool, and omit group_by for a plain per-currency total. It does not explicitly state when to prefer report over siblings like entry_list, export_csv, or invoice_summary, nor any exclusions.

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