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

With readOnly/idempotent already declared by annotations, the description still adds substantial behavior: output sorted by margin descending, truncation to 50 highest plus 50 lowest past 100 projects, companyTotals covering every project, and date attribution rules (invoices by issue date, time by work date). None of this is recoverable from annotations or schema.

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-loads the definition and result shape, then pagination, then date scoping, then example queries. Dense and mostly waste-free; the trailing question list is slightly redundant but serves retrieval matching.

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?

An output schema exists, yet the description still covers the sorting, the truncation contract, the totals scope, and the default time range — everything an agent needs to interpret results and choose parameters correctly. No material gap remains.

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 coverage is 100%, so the baseline is 3; the description earns more by explaining what from/to actually mean semantically (invoices attributed by issue date, time by work date) and by noting projectId reads any single project even when the list is truncated. It doesn't restate the date formats, which is appropriate given the schema already does.

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 specific verb+resource (per-project profitability) and pins the exact margin definition used: revenue billed in company currency against cost of time logged. That precision separates it cleanly from siblings like get_utilization_report and list_projects.

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?

Explicitly says lifetime is the default and that from/to switch to a period, and lists concrete question shapes ('which projects are profitable', 'margins last quarter') that route an agent here. It stops short of naming a sibling tool or stating when to prefer a different report instead.

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