Download invoice PDF

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

With no annotations, the description carries the full burden. It discloses that the output is base64, which is a useful behavioral detail beyond a simple 'download'. However, it does not mention error handling, permissions, or behavior for invalid/not-booked invoice numbers.

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, clear sentence that conveys the action, the target, and the output format with no unnecessary words. It is front-loaded and easily parsed.

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 tool with one parameter and no output schema, the description adequately communicates the return format (base64 PDF) and identifies the resource type (booked invoice). Minor gaps exist around error cases and the need for prior booking, but the tool's purpose and primary use are clear.

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 schema has 100% coverage and the single parameter 'bookedInvoiceNumber' is described as 'Booked invoice number'. The description adds no further meaning beyond the schema, so the baseline score 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 uses a specific action verb ('Download') with a clear resource ('a booked invoice PDF') and specifies the output format ('as base64'). It clearly distinguishes this tool from sibling tools like get_booked_invoice, which likely returns invoice data rather than the PDF file.

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?

No guidance is provided on when to use this tool versus alternatives such as get_booked_invoice or list_booked_invoices. The description does not mention prerequisites, scenarios where this is the preferred choice, or any explicit exclusions.

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