mailkite_claim_subdomain

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

The annotations already cover readOnly (false), idempotent (false), and destructive (false). The description adds meaningful behavioral context beyond the annotations: the resulting subdomain comes back already verified with an empty `dns` array, so the agent knows no DNS publishing is needed. It also notes the pool changes over time, which impacts repeated claims. A minor gap is not mentioning what happens on duplicate/conflicting label, but the provided detail goes beyond the structural hints.

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 a tight three-sentence block: it states the purpose, the behavioral guarantee (already verified), the use-case tradeoff vs createDomain, and the auth requirement. Every sentence adds distinct value and none are filler. It is front-loaded with the most decisive fact ('Claim a free MailKite subdomain') and then scaffolds the necessary decisions around the call.

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?

There is no output schema, but the description provides a clear expectation of the result: a subdomain that is already verified with an empty dns array. It also covers prerequisites (management session token, the base from suggestSubdomain), and distinguishes the use case from a custom-domain route. It doesn't spell out the exact response shape (e.g., whether it returns the full hostname) but for a single-parameter claim endpoint it is complete enough for an agent to call it 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 coverage is 100% with a thorough `subdomain` description, but the tool description enriches the meaning: it explains that the base is dynamic and should be fetched from `suggestSubdomain`, and that the label forms a full host on a MailKite-managed zone. This goes beyond the schema's character-format details and tells the agent how to obtain the required base, which is valuable context.

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 a specific verb and resource ('Claim a free MailKite subdomain') and precisely defines the object as a `<label>.<base>` host on a zone MailKite runs. It also distinguishes itself from the sibling `createDomain` by noting the difference between a managed subdomain and a bring-your-own-domain path, so an agent can immediately tell this apart from other domain tools.

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 when to use this tool ('when you want onboarding to work without asking anyone to touch DNS') and explicitly says the alternative is `createDomain` for a custom domain. It also points to `suggestSubdomain` for the current `base` and states the requirement for a management session token, leaving no ambiguity about prerequisites or alternatives.

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