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

The auth requirements (session, X-Organization-Id, CSRF) and the 409-on-conflicting-revision detail are genuinely useful additions beyond the annotations. However, 'An identical retry is idempotent' directly conflicts with idempotentHint=false, whose MCP meaning is precisely that repeated identical calls have no additional effect.

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?

Dense, short sentences with no filler; each clause carries information. It is slightly mis-front-loaded, leading with auth prerequisites rather than the action, and the DNS/settings sentences reference parameters the schema does not expose.

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 no output schema, it covers the safety-relevant ground: auth, preservation of omitted settings, idempotency behavior, and the conflict error. The completeness is undermined by describing a DNS/selectors surface that the schema does not have, leaving the agent unable to reconcile the two.

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 baseline would be 3. But the description references 'dns', 'selectors', and 'rotating_addresses' — none of which exist in the input schema, which only has id, revision, and manual_expires_on. This stale text actively misleads an agent building a call.

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 opening line states a specific verb and resource: 'Set or remove the private manual expiry.' That is clear enough to separate it from siblings like domain_status or configure_domain_monitor. It stops short of explicitly naming an alternative tool, so it does not reach 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?

It gives conditional guidance ('Send manual_expires_on, dns, or both. Omitted settings are preserved.'), which tells the agent how to shape a call, but never says when to reach for this tool versus a sibling such as configure_domain_monitor or domain_history. Usage is implied rather than scoped.

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