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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the description doesn't need to repeat safety. It instead adds non-obvious behavior: account information is not stored, and the output is a standard EMVCo payload usable by any QR library. Return shape details (prefix, CRC) are omitted but are standard for the format.

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?

The core purpose and the no-storage caveat are front-loaded in the Vietnamese sentence, which is efficient. The trailing English sentence largely duplicates it, which is a minor redundancy rather than bloat.

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 four-parameter, flat, non-networked tool with full schema coverage and annotations covering safety, the description covers purpose, optionality and downstream usage. It says nothing about the payload's format or failure modes for invalid BINs, but those are marginal for a straightforward builder.

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 the schema already explains bank (BIN or abbreviation), amount, message and account_number. The description only restates that amount and message are optional, adding little beyond structured fields; baseline 3 applies.

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 first sentence names a specific verb and resource: it creates a VietQR (NAPAS) bank-transfer QR payload string for a Vietnamese bank account, optionally with amount and message. No sibling tool (quote, VAT, pricing, referral) overlaps, and the English sentence confirms scope. An agent knows exactly what this produces.

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 tells the agent what to do with the result — feed the string into any QR-generation library — which is the key downstream step. It does not state explicit when-not conditions or alternatives, but no sibling tool offers a comparable capability, so the practical gap is small.

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