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

Annotations indicate a mutating, non-idempotent, open-world operation. The description adds crucial context: the one-time nature, the claim of the hostname ('first-to-verify wins'), the throttling of rapid re-checks, and that it initiates certificate issuance. This goes well beyond the annotations and fully discloses behavioral traits.

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 concise yet information-dense. It opens with the core action, then layers in usage constraints and behavioral notes. Every sentence adds distinct value, and there is no fluff or repetition. It is well-structured for quick comprehension.

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 single-parameter tool with a complete schema and an output schema (as signaled), the description covers all necessary operational context: when to call, what happens on success, how to handle propagation delays, and how to track progress via a sibling. Nothing an agent needs to invoke it correctly is missing.

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?

The input schema already provides a clear description for hostname ('the custom domain hostname to verify, e.g. shop.customer.com') with 100% coverage. The description does not add extra parameter-level detail, but none is needed. Baseline 3 is appropriate since the schema carries the semantic load.

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 tool's purpose: 'Check the DNS TXT challenge for a claimed domain and, on success, take the global (hostname -> tenant) binding and start certificate issuance.' It distinguishes itself from siblings like create_custom_domain (which creates the entry) and get_custom_domain (which reads status) by describing the verification and binding action.

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?

Explicitly instructs when to call ('ONCE after the human confirms they have added the DNS records'), when not to ('do NOT poll this in a loop'), and how to handle failures ('tell the human it may take a few minutes'). It also names an alternative tool, get_custom_domain, for monitoring progress. This is exemplary usage guidance.

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