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

The description notes the tool is read-only, which aligns with the readOnlyHint annotation and adds temporal context about UTC month and look-back window. However, it does not disclose potential side effects, rate limits, or pagination behavior. Since read-only is already annotated, the description adds moderate transparency but not extensive new behavioral detail.

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 description is a single, concise sentence that avoids redundancy. It states the key purpose and options without extraneous detail, making it easy to parse and understand.

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?

Given there is no output schema, the description does not need to specify return format. It provides enough context about what data is returned (spend) and the optional grouping. It lacks details on the response structure, but that is acceptable here. Overall, it is reasonably complete for its purpose.

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 description only vaguely hints at parameter meanings: 'look-back window' suggests days, and 'grouped by' explains group_by. The limit parameter is entirely unexplained, and days and group_by lack explicit definitions. With 0% schema description coverage and no parameter descriptions, the tool description should compensate more fully, but it only partially does.

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 clearly states the tool returns spend data for the current UTC month with an optional look-back window, and lists grouping dimensions. This is a specific verb-resource combination that distinguishes it from siblings like list_budgets or list_policies, which focus on other entities.

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 implies usage for spend queries but does not explicitly contrast with alternatives. An agent might infer when to use this versus list_budgets, but no direct guidance is provided. It would benefit from stating 'use this when you need spend details rather than budget or policy information.'

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