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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds genuinely useful behavior beyond that: the data is sourced from specific Cost Explorer APIs, and the granularity is one snapshot per commitment type per month, plus net-savings content.

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 sentences, front-loaded with the verb and resource; the API-mirroring note is tacked on but short. No filler, though the first sentence is dense with parentheticals.

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 no output schema, the description carries the burden of telling the agent what comes back, and it does: per-commitment-type monthly utilization/coverage plus net savings vs on-demand. Only pagination or response envelope details are absent.

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 the baseline is 4. There is nothing for the description to disambiguate at the parameter level.

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 (List) and resource (Reservation/Savings Plan utilization and coverage snapshots) and pins the source to AWS Cost Explorer's GetReservationUtilization/GetSavingsPlansUtilization. It is clearly distinguishable from cost-query siblings on inspection, though it never names its closest neighbor list_commitment_expirations to sharpen the boundary.

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 explains what the data is and where it comes from, but gives no when-to-use vs when-not guidance and does not route the agent to an alternative sibling (e.g., query_costs or list_commitment_expirations) for related commitment questions.

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