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

Annotations already declare read-only, idempotent, closed-world behavior, so the bar is lower; the description adds value by disclosing what the call surfaces (activation state and required DNS records), effectively standing in for a missing output schema. It stops short of noting error behavior for unknown/unconnected domain IDs.

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?

One sentence, front-loaded with the verb and resource, with the returned information immediately after. No filler.

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?

Adequate for a simple read-only lookup backed by rich annotations, but with no output schema the description should say more about what the returned activation states look like and how the caller should use them; the ID parameter is also unexplained.

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?

The single parameter customDomainId has 0% schema description coverage, and the description never mentions how to obtain or format the ID. The name and uuid format make it inferable, but the description contributes nothing beyond the schema.

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?

Names a specific verb+resource ('Diagnose a connected custom domain') and states what is inspected (activation state, required DNS records). It doesn't explicitly contrast with the sibling verify_custom_domain or connect_custom_domain, so differentiation is only partial.

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 word 'Diagnose' plus 'connected' implies use during troubleshooting after connection, but there is no explicit when-to-use, no mention of verify_custom_domain as the alternative, and no stated precondition such as the domain having been connected first.

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