Invoice from hours

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

With no annotations, the description carries the behavioral disclosure burden. It clearly states the side effect ('Creates... an invoice') and the result behavior ('returns a single-line invoice, converting the rate... and echoing back any entry_ids'). This gives an agent a solid sense of what will happen, though it could also mention that the invoice is not automatically marked billed until entry_mark_billed is called.

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?

Two sentences, front-loaded with the essential use case, then the key behavioral details. Every sentence adds value without unnecessary elaboration or restating the tool name.

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?

Despite a rich schema, the tool has 14 parameters, no annotations, and no output schema, so the description alone is not enough for an agent to fully understand the return shape or the full behavior across optional parameters. It explains the core case well but leaves significant context to be inferred from the schema.

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 description adds meaning for the core fields client/hours/rate and the relationships around fx_rates and entry_ids, but schema coverage is only 50% and many optional parameters (notes, due_days, tax_rate, discount_percent, issue_date) are not addressed in the description. It partially compensates for the schema gap but does not fully carry the burden for all 14 parameters.

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?

States a specific operation: 'Creates and returns a single-line invoice' for bill one client for N hours at an hourly rate. Differentiates from sibling tools like invoice_create by framing it as a 'Shortcut' for the common case, making its scoped purpose clear.

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?

Provides clear context for when to use it: 'Shortcut for the common case: bill one client for N hours at an hourly rate.' It also notes the conversion behavior when fx_rates is provided. It falls short of explicitly naming alternatives or saying when not to use it, but the context strongly implies its intended niche.

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