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

Annotations only cover the safety profile (readOnly=false, idempotent=false, destructive=false). The description adds substantive behavior beyond them: partial-update semantics (omitted ttl/proxied/priority/comment retain current values), immutability of name/type, and the risk that this rewrites live DNS in the customer's own account. No contradiction with the annotations.

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?

Four sentences, each earning its place: purpose, partial-update semantics, immutability, and the safety prerequisite. The most important behavioral fact (only passed fields change) is front-loaded immediately after the purpose.

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 non-idempotent mutation with no output schema, the description covers the partial-update contract, field immutability, and the read-then-confirm prerequisite. An agent has everything it needs to call this correctly and safely.

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 100%, so the schema already explains ttl, proxied, priority, and the id-discovery params, establishing a baseline of 3. The description goes beyond the schema by explaining the cross-parameter partial-update contract (omitted fields keep current values, so a TTL change need not restate proxied), which the per-field schema descriptions do not convey.

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+resource: 'Change what an existing DNS record points at.' It also distinguishes itself from create_cloudflare_dns_record and delete_cloudflare_dns_record by explaining that name/type cannot be changed and a delete+create is required instead. An agent can tell exactly what this does without opening the 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?

Gives explicit prerequisites and workflow: read the record with list_cloudflare_dns_records and confirm the new value with the user first. It also names the when-not case (name/type changes) and routes to the sibling workflow (delete + create). Nothing is left to inference.

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