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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds genuinely useful behavior: the auth requirement ('Cotlet API key with access to this app') and an enumeration of returned fields, which is non-obvious 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?

Well front-loaded: purpose, then return contents, then usage, then auth requirement. Slight redundancy between 'all fields, the receipt link and its report' and the following field enumeration, but no wasted filler overall.

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 correctly takes on the burden of describing the return shape and does so in detail, and it also discloses the auth prerequisite. Complete for a simple single-record read tool.

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 coverage is 100% and the single parameter is documented in-schema ('Expense ID from list_expenses'), so the schema carries the semantics. The description adds nothing about the ID format or provenance beyond what the schema already states, making baseline 3 correct.

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 (get) and resource (one expense) plus its scope ('all fields, the receipt link and its report'), which implicitly distinguishes it from list_expenses and get_report. It does not explicitly name a sibling to route against, so it sits at clear-but-undifferentiated.

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 concrete use case: 'Use it to check a single line before you change anything around it.' That tells the agent the intended context (pre-mutation inspection), but there are no explicit exclusions or named alternatives such as get_report or list_expenses.

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