mailkite_check_subdomain

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

Beyond the readOnlyHint annotation, the description adds 'cheap' (cost/performance), 'requires a management session token' (authentication requirement), and that the 'reason' field is safe to show verbatim (output safety). These are valuable behavioral disclosures that the annotations do not cover.

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?

Two concise sentences that front-load the core purpose, then add usage and behavioral context. No wasted words; every sentence adds value.

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 simple read-only check with one parameter, the description covers purpose, when to invoke, authentication requirement, and output behavior. Nothing essential is missing 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 description 'Query parameter `name`.' which is tautological. The tool description does not clarify that 'name' refers to a subdomain label, though it is implied by the tool name and purpose. The schema does the heavy lifting minimally, and the description adds no extra semantic value, so 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 description clearly states the action ('check whether a free subdomain label can be claimed') with a specific resource (subdomain label) and distinguishes it from related tools like claim_subdomain or suggest_subdomain. It is unambiguous and uses a specific verb.

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?

Provides explicit guidance to call it 'as the user types' and notes that the 'reason' field is safe to display verbatim. It does not explicitly name alternatives or conditions for not using it, but the context implies it is a pre-check before claiming. This is clear but could be strengthened by naming the sibling tool for claiming.

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