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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false), yet the description adds substantial behavior detail: line-item contents (period, amount drawn from credit, balance after), the first-hour-at-deployment rule, refunds, totals, hourly rate, and live billing status. 'Read-only' merely restates the annotation, but the surrounding detail is genuinely additive. It stops short of disclosing pagination behavior, which matters because idempotentHint is false.

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?

The critical scope ('hour-by-hour billing of one server, deleted ones included') is front-loaded in a single dense sentence; the permission and account notes are tacked on compactly. The colon-and-semicolon enumeration is slightly run-on but every clause carries information.

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 explaining the return shape and does so thoroughly (per-hour rows, amounts, balances, totals, rate, current billing flag). The main omission is pagination semantics for the two undocumented paging parameters.

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 description coverage is only 33% — serverId is documented (referencing gpucloud_list_servers) but page and pageSize carry no description in either the schema or the description. With low coverage the description is expected to compensate, and it provides no parameter-level information at all.

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 and resource (hour-by-hour billing of one server) and even scopes it with 'deleted ones included', which is a meaningful differentiator from sibling billing tools like gpucloud_get_invoice or gpucloud_list_transactions. An agent can tell exactly what this returns without opening the schema.

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?

Usage is implied by the content (server-scoped billing history with a billing:read permission), but there is no explicit when-to-use or when-not-to-use guidance and no named alternative such as gpucloud_get_invoice or gpucloud_list_transactions. The 'Requires a free GPU Cloud account and MCP key' line is a prerequisite, not a routing rule.

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