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

Annotations only say readOnlyHint=false, idempotentHint=false, openWorldHint=true; the description adds the crucial behavioral facts an agent cannot infer: the claim grants nothing until ownership is proven, the response contains exactly two DNS records (ownership TXT plus permanent routing CNAME) in dns_records, and a human must act before the flow advances.

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?

Four tightly packed sentences, front-loaded with the core action, then the critical caveat ('grants NOTHING until ownership is proven'), then the next-step routing. No filler and every sentence carries a distinct operational instruction.

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?

Covers the full call lifecycle for a non-idempotent, human-in-the-loop mutation: what is created, what comes back, who must act, and which follow-up tool to call. With an output schema present, return-value detail is already handled, so nothing material 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?

Schema coverage is 100%, so the baseline is 3, but the description adds prioritization the schema does not: slug_prefix and root_endpoint are optional 'here' and are usually deferred to update_custom_domain after verification, which steers the agent to send only hostname initially.

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?

States a specific verb+resource ('claim a custom hostname for this tenant') plus the side effect (generating a DNS challenge), and explicitly distinguishes itself from the sibling verify_custom_domain and update_custom_domain. An agent can tell exactly what this tool does and does not accomplish without opening the schema.

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?

Gives an explicit ordered workflow: present the returned DNS records to the human, wait for them to be added, then call verify_custom_domain. It also names the alternative path for slug_prefix/root_endpoint ('usually set later with update_custom_domain'), so the agent knows which params to defer and which sibling to use.

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