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

Annotations already declare readOnly, idempotent and non-destructive, so the safety profile is covered. The description adds genuine behavioral context beyond that: DNS verification and SSL activation occur automatically in the backend, and this call has no side effects on activation. Useful out-of-band behavior disclosure.

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?

Front-loads the purpose in the first sentence and is appropriately sized. Slight redundancy: 'Read-only' duplicates the annotations, and 'does not validate or activate' partially restates the prior sentence about automatic backend verification.

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?

No output schema exists, so the description must describe returns — it does list domain state, DNS records and check status. For a one-parameter read tool whose annotations carry the safety profile this is nearly complete, with the only gap being the undocumented project_id.

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 project_id has 0% schema description coverage, and the description never mentions it or explains its format/role. With one undocumented parameter the description should compensate but does not, leaving the agent to infer that project_id scopes the lookup.

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 and resource ('Get the connected/pending custom domain') and enumerates what it returns (exact DNS records, automatic check status). The 'get' scope is clearly distinct from the sibling add_custom_domain without opening either 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 clear context for use — 'safe to call for progress' implies polling for verification progress, and it clarifies the tool does not validate or activate. However, it never names add_custom_domain as the alternative for actually adding or triggering a domain, so routing 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.