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

Annotations already cover the safety profile (readOnlyHint=false, idempotentHint=false, openWorldHint=true, destructiveHint=false), and the description adds genuinely new context on top: the domain must be owned by the authenticated customer, and SRV records additionally require port and weight. It stops short of saying what happens on a conflicting existing record or whether a duplicate add errors out.

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 tight sentences with zero filler: purpose and scope first, then the type list, then the naming rules and the SRV caveat. Every sentence contributes a distinct, actionable fact.

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?

An output schema exists, so return values need not be explained, and the safety profile is annotation-covered. However, for an 8-parameter mutation with 0% schema description coverage, leaving record_ttl and record_priority entirely unexplained is a real gap an agent could stumble on.

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 0%, so the description must carry the load. It usefully explains relative-name expansion and '@' for the apex (record_name), enumerates valid record_type values, and ties record_port/record_weight to SRV. It says nothing about record_ttl (default 43200) or record_priority, leaving two of eight parameters undocumented anywhere.

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 and resource ('Add a managed DNS record') plus the ownership scope ('to a domain owned by the authenticated customer'). An agent can immediately tell this is a creation operation, though the description never explicitly contrasts it with sibling update_dns_record or configure_dns_record.

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 ownership constraint and the supported record-type list imply when this tool applies, and 'SRV records require port and weight' gives a conditional usage rule. But there is no explicit statement about when to use this versus update_dns_record or configure_dns_record, so the routing decision is left to inference from the verb.

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