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

Annotations declare readOnlyHint=false and destructiveHint=false, establishing a non-destructive write. The description adds the concrete side effect (a verification code is emailed to an admin address) and the auth requirement, which the annotations do not cover. It omits rate limits or how to continue the flow, keeping it short of a 5.

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?

Purpose is front-loaded in the first sentence, followed by a clearly separated ACCESS note. Both parts earn their place, though the parenthetical Claude Code instruction is slightly verbose.

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 flow-starting mutation with no output schema, the description covers the trigger and auth prerequisites but never points to the follow-up tools (confirm_domain_email_code, check_domain_email_status, resend_domain_email). A short next-step hint would make the flow complete.

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 the email_prefix enum fully documented in the schema (default: admin). The description only echoes the 'standard admin email address' concept, adding no new meaning about the id or the enum choices, 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+resource (start domain verification) and the mechanism (via corporate email, sending a code to an admin address). This distinguishes it loosely from credential-based verification, but it does not differentiate from the very similarly named sibling start_domain_verification or setup_domain_email, so the agent still has to guess which domain-verification entry point applies.

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 ACCESS block gives a genuine prerequisite (Proof account, authenticate or start_login first) which tells the agent when the tool becomes callable. It says nothing about when to prefer this over start_domain_verification, start_user_domain_verification, or verify_domain_with_credentials, so the sibling-selection guidance is only implied.

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