Get invoice draft

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

No annotations are provided, so the description carries the full burden. It states the basic read operation but does not disclose return behavior (e.g., what happens if the draft invoice is not found), response structure, or any authorization requirements. It adds no information beyond what the title and schema already indicate.

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, front-loaded sentence with no redundant words. It directly conveys the operation without excessive detail, making it appropriately concise for a simple fetch tool.

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 simple single-parameter fetch, the description is adequate but lacks information about the return value (no output schema exists) and error handling. It also does not clarify the distinction from get_booked_invoice beyond the word 'draft'. This is a minimal viable description but has clear gaps.

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 provides full coverage with a description for draftInvoiceNumber. The description's 'by number' adds only marginal context, as the schema already describes the parameter. With 100% schema coverage, the baseline of 3 is appropriate.

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 a draft invoice by number' uses a specific verb ('fetch') and resource ('draft invoice') with a clear lookup criterion. It distinguishes this tool from siblings like list_invoice_drafts (which lists drafts) and get_booked_invoice (which retrieves booked invoices).

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 clearly implies use when a specific draft invoice needs to be retrieved by its number. It does not explicitly state when not to use it or mention alternatives, but the context is unambiguous for a single-item fetch.

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