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

Annotations already cover the safety profile (readOnly, non-destructive, openWorld=false). The description adds genuinely new behavior: a heavy rate limit and a gating condition on when to fire. It says nothing about cost, latency, or failure modes, so not a 5.

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 short sentences with zero filler, front-loading the purpose ahead of the input requirement and the rate-limit caveat.

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 estimation tool with no output schema and fully documented parameters, the definition covers scope, inputs, and invocation constraints. The only thin spot is that the shape of the returned estimate is unspecified, though nothing suggests it is complex.

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 all nine parameters are already documented with examples and defaults. The description only restates the HS-code-or-description either/or, adding no syntax or format detail beyond the schema; baseline 3 applies.

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 ('Estimate the import duties and taxes'), scopes it ('one item shipped from the UK with SAMOS'), and the sibling estimate_shipping_price makes the duties-vs-shipping distinction obvious.

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 an explicit invocation condition ('only call when the user asks for a duties/tax estimate') plus the operational reason (heavy rate limiting), which is exactly the guidance an agent needs. It does not name sibling alternatives explicitly, so it falls just short of 5.

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