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

The description states 'Writes nothing and marks nothing', implying the tool has no side effects and is effectively read-only. However, the annotations set readOnlyHint to false, which typically indicates the tool may modify state. This is a direct contradiction. The description's behavioral claim conflicts with the annotation, so a score of 1 is required per the rubric.

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 concise, with two sentences that front-load the primary purpose. It efficiently conveys the action and the follow-up steps. The trailing 'Pro.' is unclear and adds noise, but overall the structure is tight and easily digestible.

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 tool with no output schema and all annotations false (so no safety hints), the description must fully explain behavior and return value. It clearly states the tool builds a payload and has no side effects, but it does not describe the structure of the returned payload or any error conditions. Given the simplicity of the tool, this is a moderate gap.

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 100%, and all parameters have descriptions in the schema (e.g., tax_rate, issue_date, work_order). The tool description adds minimal extra meaning beyond restating the VAT rate and the default date behavior, which are already covered by the schema. Baseline 3 is appropriate given the high 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 a specific verb and resource: 'Build an invoice_create-ready payload from the lines'. It also specifies the VAT behavior and distinguishes this tool as a preparation step before raising an invoice, setting it apart from sibling tools like work_order_create or work_order_add_line.

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?

It provides clear usage context by describing the sequence: build payload, raise invoice in the invoice server, then mark the order invoiced. This implies when to use the tool, though it does not explicitly name alternatives or exclusions. The context is sufficient for an agent to infer the intended placement.

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