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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), and the description adds genuinely useful traits beyond them: results are capped at 3 candidates per product/market, every code is non-binding, and truncated large lists are flagged per product. It does not detail the per-call request allowance mechanics beyond what the schema parameter description already says.

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 dense paragraph that front-loads what the tool does and the triggering question, then covers markets, output, and caveats. Every sentence carries information, though it could be slightly more scannable with structured clauses.

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 two-parameter, moderately complex lookup tool with an output schema present, the description covers scope, inputs, output shape capped at 3 candidates with code/description/source, and the non-binding/truncation caveats. Nothing material for correct invocation is missing.

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 baseline is 3. The description restates that products take a title and optional description and markets take UK/US, but adds little syntax or format meaning beyond the schema's own parameter docs.

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 ('Suggest candidate tariff (HS) codes') plus concrete scope ('up to 20 product titles', UK Trade Tariff and optionally US HTS). It also grounds the purpose in a user-facing question ('what HS code could this product use?'), making it clearly distinguishable from siblings like eu_duty_estimate or landed_cost_estimate.

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 clear when-to-use framing via the quoted question and explains the market selection and default ('optional markets (UK, US)', default UK per schema). It stops short of explicitly naming alternative tools or stating when not to use it, so it is strong context rather than full routing guidance.

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