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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds the annual scope and breakdown behavior, which is useful but not extensive; it does not mention aggregation details, currency, or handling of uncategorized expenses.

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 two sentences with no redundancy. The first sentence states the core function, and the second provides illustrative examples, making it efficient and well-structured.

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 the strong annotations, full schema coverage, and presence of an output schema, the description is complete enough for an agent to understand the tool's purpose and invoke it correctly. No critical gaps remain.

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 100%, so both parameters (year and category) are already documented in the input schema. The description reinforces the category concept via the example question but adds no new parameter-level detail beyond what the schema provides.

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 totals expenses for a year with by-category and by-month breakdowns, using a specific verb and resource. It also distinguishes itself from sibling tools like list_recent_expenses and get_cost_summary by emphasizing annual aggregation and breakdown dimensions.

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 provides clear usage context through example questions ('what did I spend on software this year?') and implies the tool is for annual expense summaries. It does not explicitly name alternatives or exclusions, but the context is sufficient for an agent to select it appropriately.

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