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

Annotations already declare readOnlyHint=true and destructiveHint=false. The description goes beyond annotations by explaining that all keys share the account allowance and that the current call is recorded only after its result is prepared, which is useful timing/accounting context. This does not contradict the read-only annotation since it describes system bookkeeping rather than client-facing mutations.

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?

Three dense sentences, each earning its place: the main purpose and exclusion, the account-wide allowance context, and the timing nuance. The most important information is front-loaded with no filler.

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 simple read-only tool with two optional parameters and no output schema, the description covers purpose, scope, account-level behavior, and a subtle timing detail. It could be slightly more complete by indicating pagination behavior, but the essential context for correct invocation is present.

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 0%, and the description does not mention the limit or cursor parameters at all. While the parameter names and schema constraints (default, max, min) are somewhat self-explanatory, the description adds no pagination semantics or guidance, so it fails to compensate for the schema's lack of descriptive text.

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 opens with a specific verb and resource: 'Read account operation receipts and recorded research-credit costs.' It also explicitly excludes 'the client conversation,' which distinguishes it from potential sibling confusion and clarifies its scope.

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 gives clear context for when this tool is relevant: reading usage receipts/credit costs, not conversation content. It adds an important account-level condition ('All keys share the account allowance') but does not name specific alternative tools or state when-not-to-use conditions beyond the conversation exclusion.

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