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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description adds the non-obvious default window ('default: the last 30'), the fact it returns expense ids consumed by delete_expense, and the totals that come back — genuinely additive behavioral context.

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?

Front-loads the verb and scope, then the returns and use case. The long mid-sentence field enumeration is somewhat heavy, but every clause carries information and nothing is wasted.

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 read-only list tool with an output schema, rich annotations, and 100% schema coverage, the description supplies purpose, default window, returned-id linkage and use case. Nothing an agent needs to call it correctly is missing.

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 the schema already documents to/from/userId/projectId. The description only reinforces the date-span semantics ('default: the last 30'), adding marginal value over the schema, so the baseline 3 applies.

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 ('Reads the costs') and resource ('the signed-in person recorded on their projects') with the exact scope ('over a span of days'). It also enumerates the returned fields, letting an agent distinguish it from siblings like log_expense, delete_expense and log_mileage 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?

Gives a default span (last 30 days) and anchors the use case with 'Handles "what expenses have I claimed this month?"'. It also ties to the delete tool by noting it 'returns the expense ids the delete tool takes', but names no explicit when-not-to-use or a reading alternative.

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