register_sender_domain

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

No annotations are provided, so the description must carry the full burden. It mentions that the tool 'Returns DNS records' and that after verification email sends from the custom domain, but it does not disclose potential side effects, prerequisites (e.g., domain ownership), or whether the operation is idempotent. This is insufficient for a mutation tool.

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?

Two sentences, front-loaded with the core action, then return value and effect. Every sentence is informative and efficient with no unnecessary words.

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 no output schema, the description explains the return value (DNS records) and the ultimate effect. It mentions the project context but lacks details on the verification process or what happens if the domain is already registered. Still fairly complete for a simple creation tool.

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?

The input schema covers 100% of parameters with descriptions. The tool description does not add extra meaning beyond the schema; it only reiterates that the domain is for email sending. Baseline of 3 is appropriate.

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 action ('Register a custom email sending domain'), the resource ('for a project'), and the return (DNS records). It also explains the effect after verification, which distinguishes it from siblings like 'add_custom_domain' and 'remove_sender_domain'.

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 usage for setting up custom email sending, but does not explicitly state when to use this tool versus alternatives like 'add_custom_domain'. No exclusions 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.