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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context beyond annotations: it clarifies that results are 'volume-only' estimates based on a single carton line, not stowage-accurate loading plans. This prevents the agent from over-promising accuracy to the user. The modest extra context earns a 4 given the low bar set by the annotations.

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?

Two sentences with zero wasted words. The first sentence front-loads the verb, resource, and outputs; the second pinpoints usage and exclusions. Every clause earns its place and the description is easy to scan in tool listings.

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 calculator with six well-documented parameters and a complete safety annotation set, the description is sufficient. It lists the outputs an agent can expect (CBM, weight, container counts) even without an output schema. Minor gaps like assumed container dimensions or output rounding are not critical for correctly invoking the tool.

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 description coverage is 100%, with every parameter already documented with units and meaning (e.g., 'Outer carton length in centimetres'). The description adds no parameter-specific syntax or format details beyond the schema, only reinforcing that inputs represent a single identical-carton line. This is the baseline 3 where the schema carries the weight.

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 ('Estimate') and names the exact outputs (CBM, shipment weight, volume-only 20ft/40ft/high-cube container counts) plus the input scope ('from one carton line'). It also distinguishes itself from related false-friend tools by explicitly stating it is 'not a loading simulation or a freight quote'. This gives an agent a clear, unambiguous understanding of the tool's role.

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 gives an explicit usage context ('Useful for full-container RFQ planning') and states what the tool is not ('not a loading simulation or a freight quote'). While it doesn't name specific sibling alternatives, the positive use case plus exclusions gives an agent enough guidance to select it over broader estimation or quoting tools.

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