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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so the safety profile is covered. The description adds the underlying endpoint (GET /invoices/code/{code}) and a code format example, but says nothing about error behavior when a code is not found or what the payload looks like.

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?

Two terse sentences with the resource and identifier pattern front-loaded and no padding. The telegraphic style omits a leading verb phrase, but nothing is wasted.

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 one-parameter read with annotations covering safety and no output schema, the description is minimally sufficient. It leaves the agent without any hint about the returned invoice shape or not-found handling, which is a gap for a lookup tool.

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% and the single 'code' parameter is already documented as the KiotViet invoice code. The description's example format (HD000123) is a small but useful addition; per the baseline rule for full coverage this stays at 3.

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+resource ('one invoice by invoice code') and names the identifier type, which implicitly distinguishes it from kiotviet_get_invoice (id lookup) and kiotviet_list_invoices. It never explicitly names those siblings, so 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?

Usage is only implied by the 'by code' qualifier — an agent can infer this is the lookup to use when it holds an invoice code rather than an id. There is no explicit when-to-use, when-not, or named alternative.

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