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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds genuinely new context: ordering ('newest first'), page capacity ('up to 100 bills'), status semantics, and an auth requirement (Cotlet API key with access to this app). That goes beyond what the annotations provide.

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 scope are front-loaded, then detail follows in an orderly way. Slightly verbose in places ('Returns supplier bills, newest first' partially restates the opening), but every sentence carries usable information and none is 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?

With no output schema, the description carries the return-value burden and does so well, listing the item fields, ordering, and pagination. Combined with annotations covering safety and the description covering auth, an agent has everything needed to call 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%, so the baseline is 3, but the description earns a bump by decoding the status enum — 'open means unpaid, closed means paid, debit means a negative purchase' — which the schema only lists without explaining. It adds no syntax help for due_before or supplier_id, keeping it from a 5.

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 verb and resource ('Supplier bills') plus the fields returned (supplier, dates, total, balance due), which is clear on its own. It never names or contrasts with the obvious sibling myob_list_invoices, so an agent must infer that bills differ from invoices rather than being told.

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 supplies one concrete use case ('a script can check for a bill that was already entered') and explains the status filter, but gives no when-to-use-vs-alternatives guidance and no exclusions, leaving the agent to infer when list_bills beats list_invoices.

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