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

Annotations already declare readOnlyHint=false, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds nothing beyond re-listing a few field names: it never says whether omitted fields are left unchanged (partial vs full replace), whether DNS/tracking keys must be re-supplied, or what happens to existing settings on failure.

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?

A single front-loaded sentence with no filler. It is efficient, though it spends its words repeating field names already present in the schema rather than on the missing behavioral 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 9-parameter mutation tool with no output schema, the description should cover partial-update behavior, the meaning of the key parameters, and permission requirements. None of that is present, leaving significant gaps for a write operation.

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 78%, so the schema largely documents the parameters. The description maps loosely onto track_loads/track_clicks, incoming, and dmarc_reports, but says nothing about incoming vs outgoing, inbound_key, tracking_key, or use_for_any, and does not clarify partial-update semantics for the single required id.

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 (Update) and resource (domain settings) and enumerates representative fields: open/click tracking, inbound, DMARC collection. An agent can tell it apart from create-domain, delete-domain, and verify-domain by name alone, though the description does not explicitly contrast with them.

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?

No when-to-use guidance, no prerequisites (does the domain need to exist or be verified?), and no mention of alternatives such as verify-domain or create-domain. The agent is left to infer that this is a partial-modification tool from the schema.

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