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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false, and openWorldHint=false, covering the safety profile. The description adds only the precondition that the subdomain must already exist; it says nothing about duplicate/conflicting records, what happens on failure, or whether adding the same record twice creates duplicates.

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 sentence with the action and scope front-loaded and no filler. Nothing is wasted.

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 mutation tool with four parameters, full schema coverage, and annotations, the description is thin but not inadequate. It omits preconditions and record-conflict behavior that an agent would benefit from knowing before adding a DNS record.

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 all four parameters (including the MX-only priority rule and the record_type enum) are already documented in the schema. The description adds no parameter detail beyond that, so the 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?

States a specific verb (Add) and resource (DNS record) plus a scope qualifier (to an existing subdomain), so an agent immediately knows this is a record-creation tool. It does not distinguish itself from sibling tools beyond the obvious add/delete pairing with delete_dns_record, so it falls short of a 5.

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?

There is no when-to-use guidance, no mention of prerequisites (e.g., the subdomain must already be registered), and no routing to alternatives. The only implied usage comes from the phrase 'existing subdomain,' which is a constraint rather than guidance.

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