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 that the response includes line items ('with its lines'), with no mention of error behavior for missing ids, paging, or auth requirements.

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 short sentences with zero padding, and the core operation is front-loaded before the endpoint reference. Nothing here could be cut without losing information.

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 single-record fetch with a 100%-covered single parameter and read-only annotations, most of the burden is already carried elsewhere. The description is minimally sufficient but says little about what a return record contains beyond 'its lines', which matters since no output schema exists.

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 sole parameter has its own description ('KiotViet return id', positive integer), so semantics are fully carried by the schema. The description adds no format, range, or source hints beyond what the schema already provides, making the baseline 3 correct.

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 ('One customer return by id with its lines') plus the underlying endpoint, so the agent knows it fetches a single return record rather than a list. The contrast with kiotviet_list_returns is implied by 'by id' but never stated explicitly.

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?

The phrase 'by id' implies the precondition of already having a return_id, which is the natural selection criterion against kiotviet_list_returns. However, the description never names that alternative or says what to do when only search criteria are available, leaving usage to inference.

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