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

Beyond the annotations (readOnlyHint=false, destructiveHint=false, openWorldHint=true) it discloses that the bill changes books and payables, that confirmation is requested per call by default and can be disabled for this tool, and that it reaches other people requiring user confirmation. This is rich behavioral context the annotations alone don't convey.

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?

Purpose and return value are front-loaded in the first two sentences, and the technical parameter guidance follows efficiently. The confirmation guidance is somewhat repetitive ('so it asks first,' 'you confirm each call,' 'confirm with the user before each call'), which costs a point but the content is otherwise dense and purposeful.

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?

There is no output schema, yet the description explains the return (number, tax, total, balance due), the mutation/confirmation behavior, the auth requirement, and the key parameter semantics. For a 7-parameter mutation tool, an agent has everything needed to invoke it 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 100%, setting a baseline of 3, but the description adds genuine meaning: it clarifies that layout 'service' takes free-text lines while 'item' takes item codes, and explains the duplicate-checking purpose of supplier_invoice_number. That goes an increment beyond what the schema descriptions say on their own.

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 states a specific verb+resource: 'Enter a supplier invoice as a bill with its lines and tax,' and immediately distinguishes it from a sales invoice by scope (supplier/payables). It also states the outcome (creates an open bill) and what is returned, so an agent can tell it apart from sibling tools like myob_create_invoice or myob_record_bill_payment.

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 gives clear operational guidance: pass the supplier's own invoice number so a later list_bills call can spot a duplicate, and explains the service-vs-item layout choice. However, it never explicitly states when to prefer this tool over siblings (e.g. create_invoice) or prerequisites beyond the API key requirement, leaving that to inference.

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