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

With no annotations provided, the description carries the full burden of behavioral disclosure. It discloses that the tool refuses to guess duty rates, that MPF includes a CBP floor, that HMF applies only to ocean entries, and that arithmetic is deterministic with assumptions attached. It does not explicitly state that the operation is read-only or non-destructive, but the description's emphasis on deterministic arithmetic and refusal behavior gives a clear behavioral profile.

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?

Three sentences, each earning its place: the first enumerates the calculation components, the second states the deterministic nature and attached assumptions, the third gives the critical refusal behavior. The most important operational constraint (never invents a duty rate) is front-loaded at the end of the description, and the whole text is compact with no 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 calculation tool with six parameters, no output schema, and no annotations, the description covers the key behavioral constraints: what fees are included, when HMF applies, and what happens if a required rate is missing. It does not describe the output format or whether the result includes a breakdown, but the description's enumeration of components implies the breakdown. The main gap is not stating the return shape, but the tool's complexity is moderate and the description is largely sufficient.

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%, so the schema already documents all six parameters. The description adds context for hts_base_rate_pct (the server will not guess it) and clarifies the role of ocean_entry (adds HMF), but it does not add meaning for goods_value_usd, section_232_pct, section_301_pct, or freight_insurance_usd beyond what the schema provides. Baseline 3 is 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?

The description names a specific verb ('Itemise') and a precise resource ('US landed cost'), then enumerates the exact components (duties, MPF, HMF, freight, insurance). It distinguishes itself from siblings by stating it computes from rates the user supplies, which separates it from duty_passport (rate lookup) and duty_stack_rules (rules).

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 explicitly states when to use this tool: when you have rates to supply and need a landed cost calculation. It also gives a clear exclusion: 'This tool never invents a product's duty rate' and directs the agent to the official schedule or duty_passport when the rate is unknown. This routes the agent to the correct sibling tool.

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