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

Annotations already declare this is a non-read-only, non-idempotent, open-world write. The description adds genuinely useful context beyond that: code is auto-generated when omitted, duplicates are the primary risk (hence the pre-lookup), and user confirmation is required before the write. It doesn't describe the response payload, but the safety and dedupe behavior is well covered.

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?

Three short sentences, front-loaded with the 'WRITE:' severity marker and the required-parameter fact, then the operational guidance, then the endpoint. Every clause carries information; no filler.

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 10-parameter mutation with no output schema, the definition covers the operation, the required field, auto-generation behavior, and the confirmation/dedupe workflow. The one meaningful gap is what comes back from a successful create (customer id or code) so the agent can chain a follow-up call. Otherwise it is complete enough to invoke correctly.

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 100%, so all 10 parameters are already documented in the schema. The description only reinforces two of them (name required, code auto-generated), which is helpful emphasis but adds no syntax, format, or constraint detail the schema doesn't already carry. The baseline 3 applies when the schema does the heavy lifting.

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 opens with an explicit 'WRITE:' marker and states the specific verb and resource: create a new customer in the shop. That verb+resource pairing is easily separable from the get_/list_ siblings that share the customer domain. Nothing here restates the tool name tautologically.

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?

It gives concrete preconditions: confirm with the user first, and look up by phone before creating a duplicate. That establishes when-and-how to call it, including a de-duplication workflow. It stops short of naming the specific alternative tool (kiotviet_get_customer_by_code), so the agent must infer which sibling to use for the lookup.

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