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

Annotations already mark destructiveHint=true, but the description adds valuable context: the tool 'reports what went,' the receipt FILE stays on disk, and deleting a rebilled expense loses invoice-charge history. These behaviors go beyond the structured annotations and help the agent anticipate consequences.

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 concise sentences, each carrying meaningful information: the action, a key side effect, and a critical exception. No filler or redundancy; the most important information is front-loaded.

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 one-parameter delete operation, the description covers the core action, the post-action report, the side effect on files, and the rebilled-expense exception. Combined with annotations, the agent has everything needed to invoke the tool correctly and safely.

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 input schema has only one parameter, 'id', with no description (0% coverage). The description's phrase 'by id' clarifies that the id is the expense identifier, not a file or other entity. While minimal, this is sufficient for a single-parameter tool and compensates for the schema gap.

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 states a specific verb and resource: 'Delete one expense by id.' It also distinguishes itself from the sibling expense_update, clarifying what this tool is not for. The purpose is immediately unambiguous.

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?

Explicitly provides a when-not-to-use case: 'Deleting a rebilled expense loses the record of what an invoice charged, so correct it with expense_update instead.' It also notes the receipt file remains on disk, which helps an agent decide whether this tool is appropriate.

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