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

Annotations already declare a safe, idempotent, read-only calculation, so the bar is low; the description still adds real value with the divisor conventions (5000 air / 6000 ground) and the billing rule that makes the result actionable. It does not disclose whether the returned value is pure dim weight or the billable max, and it names a 'divisor' input that no annotation or schema confirms.

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?

Four tight sentences, front-loaded with the core purpose and formula constants; almost every clause earns its place. The final list_bundles sentence is the one piece of 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?

For a read-only calculator with an output schema, the description covers purpose, units, and divisor conventions adequately. The remaining gap is that actual_kg appears in neither the input list nor as an explanation of how it influences the result.

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. The description adds unit meaning (cm, kg) and divisor conventions, but it omits the required actual_kg parameter from its own input list and describes a 'divisor' input that does not exist in the schema — a mixed signal rather than a net additive explanation.

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+resource ('Compute volumetric (dimensional) weight for shipping') and immediately distinguishes itself from the many volume/shipping siblings by naming the shipping-billing concept. An agent can tell this apart from calculate_volume or calculate_international_shipping without opening a schema.

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?

'Carriers bill the higher of actual and dim weight' gives real context for why/when to run it. The trailing 'See list_bundles for related finance-universal calculators' is an odd, weakly relevant routing hint and there is no explicit when-not guidance, so it stops short of a 5.

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