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

No annotations are provided, so the description shoulders the full burden of behavioral disclosure. It states that the tool creates a draft invoice that is editable and deletable, which is key. However, it does not describe potential side effects (e.g., whether it marks hours as invoiced), required permissions, or idempotency behavior. The behavioral transparency is adequate but could be enhanced.

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 extremely concise: two sentences totaling ~25 words. The first sentence states the core purpose with precise verb and resource ('Generate a DRAFT invoice'), and the second adds critical behavioral context (editable, deletable). Every word contributes meaning; there is no redundancy or filler.

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 has 8 parameters (3 required) and no output schema, the description covers the primary function and output state. However, it lacks information about return values (e.g., invoice ID or status), error conditions (e.g., missing approved hours), or prerequisites (e.g., customer existence). The description is sufficient for basic understanding but incomplete for full contextual guidance without additional documentation.

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?

With 100% schema description coverage, the baseline is 3. The description adds context that the invoice is based on 'approved billable hours', which indirectly explains the purpose of parameters like customer_id, period_start, period_end, and grouping. However, it does not elaborate on parameter semantics beyond what the schema provides. The parameter meaning is clear from the schema, so no additional value is added.

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 the tool's purpose: generating a DRAFT invoice from approved billable hours over a billing period. It specifies 'draft' to differentiate from final invoice tools like issue_invoice, and explicitly mentions the input source (approved billable hours) and the scope (billing period). This distinguishes it from sibling tools such as create_credit_note or void_invoice.

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 explains that the draft is editable and deletable before issuing, which guides usage post-generation. It does not explicitly state when to use this tool versus alternatives (e.g., issue_invoice), but the context of sibling tools and the focus on 'draft' implies its purpose. The mention of editability and deletability provides clear guidance on the tool's output state.

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