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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the agent knows this is a destructive write. The description adds the nuance 'clean up the platform-side hostname registration when possible,' which is a useful behavioral detail beyond the annotations. However, it does not fully disclose potential side effects (e.g., whether it is reversible, impact on other domains), but given the annotation coverage, a score of 3 is appropriate.

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?

The description is a single sentence that directly states the primary action and a secondary cleanup step. It is front-loaded with the main verb and resource, with no wasted words. This is an efficient and well-structured description.

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?

The tool is relatively simple (2 params, no output schema) and the description, combined with the schema and annotations, provides enough information for an agent to call it correctly. It may lack explicit edge-case guidance (e.g., what happens if no domain is configured), but given the overall simplicity and existing structured data, it is nearly complete.

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%, meaning both app_id and domain have clear descriptions in the schema, including that domain is optional and omitting it removes the current custom domain. The description adds no extra parameter meaning beyond what the schema already provides, so the baseline of 3 applies.

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 clearly states a specific action ('Remove the configured custom domain from the app') and a distinct resource (custom domain), which immediately distinguishes it from sibling tools like add_custom_domain and set_primary_domain. It also adds a secondary detail about cleaning up hostname registration, reinforcing its unique purpose.

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 description clearly implies when to use this tool: to remove the custom domain. It does not explicitly exclude alternatives, but given the straightforward nature of the action and sibling names, the usage context is unambiguous. No exclusions are stated, but it is clear enough for an agent to select it appropriately.

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