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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior, so the bar is lower. The description adds genuine value beyond them by disclosing the accepted code lengths (4/6/8/10 digits) and enumerating the returned data points (Section 301 status in particular).

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?

A single front-loaded sentence opening with the usage trigger, followed by the input format, examples, and return payload. No filler sentences and no redundancy with the title.

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?

With no output schema, the description correctly enumerates what is returned, and annotations cover the safety profile, so an agent has enough to call this correctly. The only gap is routing: it doesn't say what to do when the user has a partial or keyword description instead of a code.

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 0% for the single 'code' parameter, so the description must compensate. It does: it specifies that the code may be 4, 6, 8 or 10 digits and provides two concrete examples (8516.60.40, 9503000071), which clarifies accepted format in a way the bare string schema does not.

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 (lookup) and resource (HTS/HS tariff code duty rates) plus the exact payload returned: duty rate, Section 301 status, units, official description. However, it never names or contrasts itself with the sibling search_hts, so sibling differentiation is left to inference.

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 a clear triggering condition: 'when the user gives an HTS / HS tariff code ... and wants the US duty rate...'. It also implicitly rules out keyword-style queries by requiring a concrete code. No explicit exclusion or pointer to search_hts for the non-code case, so it stops short of 5.

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