Add sending domain

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

Goes well beyond the annotations: it discloses that the call returns DKIM/SPF records the caller must place in DNS, and — critically — that using an API key bypasses the dashboard's admin-role check, granting authority a non-admin member lacks. The annotations only assert write/non-idempotent/open-world; this privilege-escalation caveat is exactly the kind of extra context the description should carry, and nothing contradicts the 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?

Bold section labels front-load purpose, exclusion, return value, and caveat, so an agent can scan to the needed fact. No redundant sentences; every line carries distinct information.

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 write tool with no output schema, the description covers the return content, the routing to the verify sibling, and an auth caveat. The only real gap is the undocumented projectId parameter, which neither description nor schema explains.

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?

Two required parameters with only 50% schema coverage (projectId carries no schema description), yet the description says nothing about either parameter — not even which project the domain attaches to. The domain field's bare-name rule is documented in the schema, but the description adds no meaning over the structured fields.

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 ("Register a new sending domain") and immediately disambiguates from the nearest sibling by name: "Not for: Re-checking a domain already added — that is plunk_verify_domain." An agent can differentiate add vs. verify vs. list/delete without opening any schema.

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?

Explicit "Use when" condition ("Setting up a new from address on a domain Plunk does not yet know about") plus an explicit "Not for" exclusion routing to plunk_verify_domain. Both when-to-use and when-not-to-use are covered.

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