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

With no annotations, the description carries the transparency burden. It discloses that the tool creates a persistent draft in Xero and returns line totals and tax amounts for review, making the side effect and review workflow clear. It does not mention pitfalls like cleanup or rate limits, but the core behavior is transparent.

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?

A single, well-structured sentence that front-loads the purpose and includes the key output information. Every word earns its place; no filler or redundancy.

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?

The tool is moderately complex with 8 parameters, but the schema covers all parameter details. The description provides necessary context about the draft status and return values (line totals and tax amounts), which is especially useful since there is no output schema. Slightly more detail about the draft lifecycle or error conditions would make it fully complete.

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 input schema has 100% description coverage for all parameters, so the schema already provides full meaning. The description adds minimal parameter-level insight beyond the schema, such as implying VAT preview behavior through tax categories, but does not elaborate on specific 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?

The description uses a specific verb and resource: 'Create a DRAFT invoice in Xero'. It clearly distinguishes from sibling tools like send_invoice by emphasizing 'draft' and 'before sending'.

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 conveys the intended usage context: creating an invoice for review before sending. It does not explicitly name alternatives or exclusions, but the draft/review framing makes the appropriate use case clear.

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