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

The annotations already indicate readOnlyHint=false (write operation), idempotentHint=true (safe to retry), and destructiveHint=false. The description adds the activation aspect, which is useful but doesn't provide additional behavioral detail beyond what annotations state. It doesn't disclose what happens if DNS doesn't resolve or if activation fails, but that's minor given the idempotent and non-destructive 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 concise: two sentences, with the action first and a direct usage instruction. Every word adds value, and it is front-loaded with the core purpose before the usage note. No fluff or repetition of schema details.

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?

The description is sufficient for a two-parameter tool with a clear schema and idempotent annotations. It covers the action, the trigger, and the source of parameters. It lacks details on failure handling or return values, but no output schema exists, so that's expected. It's complete for most agent use cases.

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 description coverage is 100%, so the schema already provides full parameter details, including the source of domain_id and workspace_id semantics. The description adds the context that domain_id is from add_custom_domain or list_custom_domains, which reinforces the schema. Since coverage is high, the baseline is 3, and the description's emphasis on the follow-up role earns a 4.

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: to re-check DNS records and activate a custom domain once they resolve. It uses specific verbs ('Re-check', 'activate') and a specific resource ('custom domain's DNS'). It distinguishes itself from add_custom_domain by implying it is a follow-up action, though it doesn't explicitly name the sibling.

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 provides clear guidance on when to call this tool: 'Call after adding the DNS records that add_custom_domain returned.' This gives a strong contextual trigger. It doesn't explicitly state when not to use it or mention alternatives like remove_custom_domain, but the primary usage condition is well-defined.

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