mailkite_create_domain

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

Annotations only supply readOnlyHint=false, idempotentHint=false, and destructiveHint=false, which tell the agent little. The description adds meaningful behavior: the return includes DNS records, provider behavior depends on plan, and a management session token is required. It would be even better if it explained idempotency/duplicate handling, but the description is fairly informative beyond the annotations.

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 description is three sentences and front-loads the primary action and return value. The second sentence packs a lot of plan/parameter information into one sentence, which is somewhat dense but not bloated. Every sentence earns its place, though the mention of email_provider_id creates confusion.

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 low-complexity tool with one parameter and no output schema, the description covers about returns, auth, and plan behavior. However, the missing/extraneous parameter mismatch (email_provider_id in description but not schema) is a serious gap that prevents correct invocation, and it never explains how the parameter should be formatted or what additional setup (DNS verification, existence pitfalls) follows creation.

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 0%: the only parameter, `domain`, is not described at all. Worse, the description references `email_provider_id` and tells callers they 'may pass' it, but the input schema does not include that parameter, so an agent following the description would send an invalid request. This is misleading and harms correct invocation.

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 uses a clear action verb with a resource — "Add a domain" — and adds that the tool returns domain plus DNS records, which distinguishes it from many sibling tools. However, it does not explicitly differentiate from mailkite_register_domain or verify-related siblings, so it is just short of a 5.

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 description gives useful contextual guidance: it says the tool requires a management session token, and explains how provider selection works on paid vs. free plans with a pointer to listEmailProviders. There is no explicit "when to use this vs register_domain or verify_domain", so the agent is left to infer the boundary between these siblings.

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