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

Annotations already declare readOnly, idempotent, non-destructive, and open-world, so the safety profile is covered. The description adds real context beyond that: the response mixes two economically distinct figures, one billable by rent.dev and one merely a showback of vendor billing, which prevents an agent from treating BYOK figures as rent.dev charges.

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 front-loaded sentence with the default window parenthesized early. The trailing clause 'beside showback of BYOK usage your vendors bill you for' is slightly tangled but each phrase carries a distinct fact.

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?

With only two optional parameters, full schema coverage, annotations, and an output schema, the description covers scope, defaults, and the composition of the result. Nothing critical is missing, though a pointer on granularity or aggregation would round it out.

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% and both fields already document RFC 3339 formats with their own defaults. The description restates the 30-day default but adds no format, timezone, or boundary-inclusivity guidance beyond the schema, so baseline 3 applies.

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 pair (usage over a period) and goes further by naming the two reporting concepts it returns: rent.dev-billed sandbox usage and BYOK showback. That distinguishes it from rent_get_balance, though it never names the sibling explicitly.

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?

Implies usage via 'over a period' and gives the default window, but never says when to reach for this versus rent_get_balance (current balance) or rent_quote (pricing). The agent must infer the split from the nouns alone.

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