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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds real business context beyond that – VAT invoices in VND, Vietnamese-language support, and the product lines covered – but says nothing about response shape, whether data is static or fetched live, or how the lang option changes the output.

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?

One dense sentence with the resource named first and supporting detail (currencies, VAT, language, product lines) packed into parentheses. Nothing is redundant, though the parenthetical product list is slightly heavy for a contact-lookup tool.

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?

This is a simple, single-parameter, read-only lookup with no output schema, and the description covers the essentials of what the tool is about. It is still incomplete on two points an agent would want: what the returned contact/service data actually contains, and the effect of the only parameter.

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 0% for the single 'lang' parameter, so the description must carry the burden and largely does not. The phrase 'Vietnamese-language support' hints at a language dimension, but it never states that 'lang' selects the language of the returned information or what 'en' versus 'vi' yields.

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 the specific resource (Vietnis, a Vietnam-based reseller) and enumerates what it exposes: contact details and services. It also ties itself to the sibling estimation tools by noting its prices appear in 'these estimates', which orients the agent. It falls short of a 5 only because it doesn't explicitly contrast itself with any specific sibling tool.

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?

Usage is only implied: an agent can infer this is the lookup to call when a user asks who the reseller is or wants to contact them after seeing an estimate. There is no explicit statement of when to call it, when not to, or what to do instead, and no mention of whether it should be called before or after an estimation.

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