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

Beyond the annotations it discloses auth prerequisites (account session, X-Organization-Id, CSRF for writes), conflict handling (a conflicting revision returns 409), preservation of omitted settings, and notification behavior for rotation vs alias changes. One nuance: it says 'an identical retry is idempotent' while annotations declare idempotentHint=false; this reads as a refinement (guarded by the revision field) rather than a flat misstatement, and the destructiveHint=true annotation is consistent with a settings-overwriting write.

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?

Nearly every sentence carries factual load (auth, idempotency, 409, preservation), so there is little filler. However, it is a chain of telegraphic fragments that opens with prerequisites instead of the purpose, so the reader must assemble the tool's function from the name and scattered clauses.

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 destructive, nested-object, no-output-schema tool this covers the essentials an agent needs: auth requirements, revision/conflict semantics, partial-update behavior, and the scope exclusions. It would be fully complete if it resolved the manual_expires_on discrepancy and clarified what the write replaces.

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 the schema already documents id, revision, and the nested dns object, making 3 the baseline. The description restates the dns requirements and adds 'omitted settings are preserved,' but it also references 'manual_expires_on,' a setting that does not appear anywhere in the input schema, which introduces confusion rather than meaning.

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?

The description states a concrete verb+resource (set DKIM selectors and IP-rotation expectation for a domain's DNS) and draws boundaries against siblings by saying it 'does not discover selectors, enable monitoring or authenticate sent messages,' which implicitly separates it from configure_domain_monitor and domain-verification tools. It is clear, though the core purpose is threaded between prerequisites and constraints rather than stated up front.

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?

It gives explicit conditional guidance: 'Send manual_expires_on, dns, or both. Omitted settings are preserved,' and states the DNS payload 'requires both selectors and rotating_addresses.' It also lists what the tool does not do. It stops short of naming a specific alternative tool to use instead, so it is context-rich but not a full when/when-not routing table.

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