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

With no annotations provided, the description carries the full burden. It discloses that totals, VAT, and rounding are computed server-side, plus credit cost and API key requirement. It does not mention output format or error handling, but the given behavioral details are valuable.

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 two sentences: first states purpose, second lists mandatory inputs and cost. Every sentence adds value, front-loaded with the core action, and there is no redundant content.

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?

Given the tool's complexity (10 params, nested objects, no output schema), the description covers purpose, required fields, key subfields, server-side computation, and cost/auth. It could additionally mention the output format or optional parameters, but it is still sufficient for an agent to select and invoke the tool correctly.

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 coverage is low (20%, only issueDate and buyerReference descriptions). The description compensates by specifying mandatory fields and breaking down subfields for lines (name, quantity, unitPrice, vatRate) and sellerContact (name/phone/email), which is not present in the schema.

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 a specific verb 'Generate' with a specific resource 'German XRechnung 3.0 e-invoice' and format details (UBL 2.1, EN 16931). It distinguishes from siblings 'extract_invoice' and 'validate_invoice' by implying a creation action.

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 the tool is for creating an XRechnung from JSON, contrasting with extraction and validation siblings. While it doesn't explicitly name alternatives or exclusions, the context is strong enough that a user would know when to use it.

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