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

Annotations already declare the write/non-destructive/non-idempotent profile, so the bar is lower. The description adds genuinely useful context beyond them: the call returns CNAME and TXT records the customer must place at their DNS provider, and verification is not part of this call.

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?

Three short sentences, front-loaded with the action, then the return payload, then the workflow boundary. Every sentence conveys information an agent needs; nothing is padding.

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?

With no output schema, the description correctly carries the return-value burden by naming the CNAME/TXT records. For a two-parameter additive tool with full schema coverage and annotations, this is nearly complete, though it does not say what happens if the domain is already connected.

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 both parameters are already documented (including the help.acme.com example, which the description merely repeats). The description adds no format, constraint, or hostname-validation detail beyond the schema, so the 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?

States a specific verb (connect) and resource (a customer domain to a hosted product's help center), with a concrete example (help.acme.com). It implicitly distinguishes itself from the similar-sounding add_mail_domain/add_redirect siblings by scoping to the help center.

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 final sentence 'DNS verification is a separate action' tells the agent this tool does not complete the workflow and routes the verification step elsewhere. It does not explicitly name check_help_center_domain or state when not to use it versus add_mail_domain, so it stops short of full guidance.

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