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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds only the raw endpoint path 'GET /customers/code/{code}', which merely restates the read-only nature and says nothing about behavior when the code is not found or what the single-object response 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?

Extremely short and front-loaded with the purpose. The second sentence repeating the HTTP route is low-value padding, but nothing else 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 simple one-parameter read whose annotations cover the safety profile, this is minimally sufficient. It nonetheless leaves the agent without the not-found behavior or any hint of the returned object, which matters because there is no output schema.

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?

Single parameter with 100% schema description coverage ('KiotViet customer code.'), so the schema carries the burden and the baseline is 3. The description confirms the lookup is by code but adds no format, casing, or uniqueness semantics beyond the schema.

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?

It identifies the resource (customer) and the lookup key (customer code), which implicitly distinguishes it from kiotviet_get_customer. But 'One customer by customer code' is a terse fragment with no verb, and it never names the sibling it replaces, so the agent must infer the distinction from the sibling's name alone.

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?

There is no statement of when to use this versus kiotviet_get_customer, kiotviet_list_customers, or the other *_by_code siblings. The agent gets no condition, no prerequisite, and no exclusion.

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