Thêm domain gửi email

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

Annotations already declare readOnlyHint=false, destructiveHint=false, openWorldHint=true and idempotentHint=false, so the safety profile is largely covered. The description adds two useful pieces beyond that: the return value (DNS records) and the security note that the Cloudflare token is not stored. It does not disclose auth requirements, what happens if the domain already exists, or that the annotation says the operation is not inherently idempotent even though an idempotency_key is accepted.

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 purpose, return value and alternative are front-loaded in two short clauses with no filler, and the Cloudflare caveat is placed immediately after the output note where it is relevant. The bilingual duplication costs some density but is presumably intentional for the audience.

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 mutation tool with no output schema, the description usefully states that DNS records are returned and points to the Cloudflare path. However, it omits the natural next step (mail_domain_verify), duplicate-domain behavior, and any error or prerequisite context, leaving the agent to infer the post-add workflow from sibling names.

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 exactly 50%: idempotency_key is documented in the schema (reuse within 24h for retries) while domain has no description. The description adds no parameter-level meaning for either, so it neither compensates for the gap nor enriches the documented key. Baseline 3 is appropriate here.

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 English clause states a specific verb and resource ('register a sender domain and get DNS records'), and the Vietnamese notes the outcome ('Trả record DNS'). It also distinguishes itself from a sibling by naming mail_domain_cloudflare for Cloudflare users. The only weakness is the slightly circular opening ('Khi gửi bằng domain của app, thêm domain').

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 explicitly routes to an alternative with a concrete condition: if the user uses Cloudflare, call mail_domain_cloudflare with their token (not stored). That is real when-to-use-the-other-tool guidance. It does not say where this fits in the flow relative to mail_domain_verify or note prerequisites such as an active mail plan.

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