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

Beyond the annotations, the description discloses that each country consumes the user's read quota, that the comparison is persisted to their history, and that failed reads are flagged. It also explains the partial-result contract: comparable=false, a comparison_note explaining why, and no cheapest country. Only auth requirements and any rate-limit specifics are left unsaid.

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?

Front-loaded with the core action and the cheapest-first ordering, and nearly every sentence carries information about behavior or output. The mid-sentence 'plan:' fragment is slightly awkward and interrupts the flow, but nothing is redundant.

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 still conveys return shape: per-country local price converted to USD, stock, source of each read, cheapest-first ordering, a comparable flag, and a comparison_note on non-comparable results. For a three-parameter, non-idempotent, open-world tool, an agent has everything needed to call and interpret it.

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%, so the description has to carry all three parameters, and it does: countries are two-letter codes like US/GB/JP, plan is the exact subscription plan or billing period and maps to a product variant, and link is the product URL whose format determines store resolution. Missing only concrete examples of accepted plan strings or a country-count limit.

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 gives a concrete verb and resource: read the same product page from inside other countries and compare local price converted to USD, cheapest first, including stock and read source. That is far more specific than the title alone. It does not name the near sibling compare_stores or subscription_prices, so an agent still has to infer which tool to pick.

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?

Implied usage is clear (Apple and LEGO links resolve to each country's store), and the plan parameter's default behavior is spelled out. But there is no explicit when-to-use or when-not-to-use guidance versus compare_stores, subscription_prices, or plain read for a single country, and no stated prerequisites.

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