Get booked invoice

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 only says 'Fetch', which implies a read operation, but it does not disclose error handling (e.g., not found), required permissions, or response structure. This leaves significant behavioral gaps.

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 wording. It efficiently communicates the tool's purpose and fits the simplicity of the 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 tool, the description covers the core purpose and input. However, it lacks details on return values, error behavior, and usage context. Since there is no output schema and no annotations, the description is minimally adequate but with 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 schema fully documents the only parameter (bookedInvoiceNumber) with type, description, and constraint. The description's 'by number' reiterates the schema without adding extra meaning, so the baseline of 3 applies due to 100% schema coverage.

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 clearly states 'Fetch a booked invoice by number' with a specific verb ('fetch'), a specific resource ('booked invoice'), and the identifier method ('by number'). This distinguishes it from sibling tools like get_invoice_draft and list_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 usage is implied: you use this tool when you have a booked invoice number and need the invoice details. However, there is no explicit guidance on when to use this vs alternatives like list_booked_invoices or get_invoice_draft, nor any exclusions or conditions.

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