get_invoice

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

Annotations already declare the tool as readOnly, idempotent, and non-destructive, so the safety profile is well-covered. The description adds no behavioral context beyond the tool's basic function, such as potential 404s, the effect of the 'include' parameter, or response structure. This is acceptable given the strong annotations, but the description itself does not enhance transparency.

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 short sentence that conveys the essential purpose without any fluff. It is appropriately front-loaded and every word earns its place. No unnecessary information is included, making it an exemplary model of conciseness.

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?

The tool is simple: one required param and one optional param, with an output schema present and clear annotations. The description, while minimal, covers the fundamental purpose of the tool. The presence of an output schema eliminates the need to describe return values. It does not address the 'include' parameter or edge cases, but for a get-by-id operation, the description is reasonably complete.

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 0%, so the description must compensate for explaining parameters. It only says 'by id', which merely restates the invoice_id property already in the schema. The 'include' parameter is completely unexplained, and no additional meaning is added beyond what the schema already provides. This is a significant gap for a tool with two parameters, especially one optional field.

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 'Fetch one invoice by id' clearly states a specific action (fetch) on a specific resource (invoice) with a precise scope (by id). It distinguishes itself from sibling tools like search_invoices, which lists or searches for invoices, whereas this tool retrieves a single one. The verb+resource+scope construction is unambiguous and high-quality.

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 no explicit guidance on when to use this tool versus alternatives. It does not state 'use this when you have an invoice ID' or mention that search_invoices should be used when you don't have an ID. The implied use case (having an ID) is present, but there is no clear context or exclusion, so the tool offers minimal usage direction.

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