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

Annotations already declare idempotentHint=true and destructiveHint=false, and the description adds the exact idempotency key (same type, name and value) rather than just repeating the flag. It also discloses the TTL propagation delay, a behavior an agent needs to set expectations after the call, and notes the MX priority requirement. It stops short of saying what happens on conflicting or invalid records.

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?

Three short sentences: purpose, supported types, then idempotency and propagation caveats in descending order of importance. No filler, and the most decision-relevant facts are front-loaded.

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 purpose, allowed types, idempotency and propagation, which is most of what an agent needs. It leaves open whether the call returns the created record or an identifier, and what failure modes exist for conflicting records.

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 description coverage is 100%, so every parameter including ttl, prio, name and value is already documented in detail. The description's only added parameter detail is "MX (needs prio)", which the schema states verbatim, so 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?

Opens with a specific verb and resource ("Add a DNS record to a domain") and scopes it to domains in this account, which cleanly separates it from list_dns_records, delete_dns_record and the domain/order siblings. It does not explicitly name any sibling, but the operation is unambiguous from the verb alone.

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?

"Safe to repeat" effectively tells the agent it does not need to call list_dns_records first to check for duplicates, which is real usage guidance. However there is no explicit when-not guidance, no statement that the domain must already be owned/registered in the account, and no routing to check_domain or list_dns_records before adding.

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