register_sender_domain

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

With no annotations, the description carries full burden. It discloses that the tool returns DNS records (DKIM CNAMEs + SPF/DMARC) to add and that after verification, emails send from the custom domain. It does not mention potential issues like domain ownership verification time or error cases, but it provides essential behavioral context.

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 two sentences, front-loaded with the primary action and outcome. Every sentence adds value without unnecessary repetition.

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?

Given the tool's complexity (email domain registration requiring DNS record setup) and no output schema, the description explains the return value (DNS records) and post-verification effect. It lacks information about verification steps or prerequisites, but is largely 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 both parameters described. The description adds no further meaning beyond the schema; it only restates the parameters. Baseline 3 is appropriate as the description does not enhance parameter understanding.

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 verb 'Register' and the resource 'custom email sending domain for a project'. It distinguishes from sibling tools like 'add_custom_domain' (general custom domains) and 'check_domain_status' (status checking) by specifying email-sending context and the act of registration.

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 implies the tool is used when wanting to set up email sending from a custom domain, but it does not explicitly state when to use it versus alternatives (e.g., 'sender_domain_status' for checking existing domains). No when-not-to-use or prerequisites are mentioned.

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