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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered. The description's added value is defining what 'unbilled' means (tracked but not yet invoiced), which is genuinely useful domain context, but it says nothing about aggregation, time range, or output shape.

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?

A single short sentence that front-loads the core concept and ends with the grouping scope. No wasted words, though the brevity borders on under-specification rather than tightness.

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 zero-parameter read tool this is close to adequate, but there is no output schema, so the agent cannot tell whether the result is a per-project total, a list of time entries, or a nested breakdown, nor whether any date window applies. One more clause on return shape would make it complete.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate. Baseline 4 applies; no parameter-level gaps exist to compensate for.

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 names a specific resource (hours tracked but not invoiced) and adds the key scope qualifier 'per project,' which clarifies the grouping. It is clear what the tool reports, though it does not explicitly differentiate itself from adjacent tools like get_revenue, get_project_budget, or list_time_entries.

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?

There is no explicit when-to-use guidance and no named alternative. The agent must infer that this tool is for unbilled-time reporting rather than invoicing (create_invoice_from_time) or raw entry listing (list_time_entries). The definition gives a definition of the metric but no routing guidance.

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