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

Annotations already declare readOnlyHint=true, destructiveHint=false and closed-world, so the safety profile is covered. The description adds useful scoping semantics (completed/closed status, billable, no invoice present), but says nothing about result volume, pagination, or ordering for what is presumably a list result.

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 short sentences, no filler, with the scoping definition front-loaded before the usage triggers. Every clause earns its place and nothing is redundant.

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 no-parameter, read-only list tool this is nearly sufficient: purpose, scoping, and usage intent are all present. It is docked only because the description is the sole source of return-shape information (no output schema exists) and says nothing about what the result actually contains or how large it may be.

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 and the schema is empty, so there is nothing for the description to disambiguate; baseline 4 applies. The description's implicit statement that filtering is baked in (all completed/closed unbilled billable jobs, no arguments) helps the agent understand the call is argument-free.

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 precise resource set: completed/closed billable jobs that have no invoice yet, with the parenthetical 'ready-to-invoice candidates' crystallizing intent. It is far more specific than a tautology, but it never explicitly differentiates itself from the very close sibling unbilled_jobs_for_tech or from find_jobs/find_invoices.

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?

It gives concrete usage triggers in quoted user phrasing ('what can we invoice', 'unbilled jobs'), which is exactly the kind of intent matching an agent needs. It does not, however, state when NOT to use it (e.g., when a per-technician breakdown is wanted, use unbilled_jobs_for_tech), so the exclusion half of the guideline is missing.

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