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

Annotations already declare readOnly/idempotent/non-destructive, so the description doesn't need to re-state safety. It instead adds value by disclosing what comes back — line items, dates, total, balance due, status — which matters because no output schema exists. It doesn't cover failure behavior (e.g. unknown bill_id).

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?

One short sentence with no filler, and the identifying noun leads. It reads as a fragment rather than a statement of action, which slightly blunts front-loading but wastes nothing.

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?

For a simple single-record read with full annotation coverage, the description plus schema covers what an agent needs to call it. Only the not-found/error case and the relationship to get_invoice are left unstated.

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% and the schema already says bill_id comes from list_bills, so the single parameter is fully documented. The description adds no format or validation detail beyond that, making a baseline 3 appropriate.

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?

Identifies the resource precisely (a single vendor bill, contrasted with the sibling list_bills) and enumerates the payload it returns. No explicit verb, but 'One vendor bill' plus the required bill_id makes retrieval unambiguous.

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?

Gives no when-to-use guidance and never names the relevant siblings (list_bills, get_invoice, get_purchase_order) as alternatives. The only routing hint, 'bill_id from list_bills', lives in the schema rather than the description.

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