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

Annotations already declare destructiveHint=true, idempotentHint=false, and readOnlyHint=false, so the safety profile is known. The description adds genuinely new context: the app and its AppDeploy URL remain available and DNS records at the provider are unchanged, which bounds the blast radius. It stops short of noting error behavior on a non-existent mapping, which matters given idempotentHint=false.

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?

Three short sentences, front-loaded with the action and its scope, followed by usage gating and side-effect boundaries. No sentence is redundant.

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 two-parameter tool with no output schema, the description covers purpose, usage condition, and what is preserved. The only gap is that it does not address failure behavior (e.g., removing a mapping that does not exist) despite idempotentHint=false.

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% with only two parameters, so the schema already documents app_id and domain. The description reinforces that domain is a hostname mapping scoped to the app but adds no format or syntax detail beyond that. Baseline 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?

States a specific verb and resource ('Remove a hostname mapping from this app') and clarifies the effect on AppDeploy routing. This cleanly separates it from add_custom_domain and verify_custom_domain in the sibling list.

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?

'Use only when the user asks to remove that domain' gives an explicit when-to-use condition and implicitly warns against speculative invocation. It does not name an alternative tool (e.g., verify_custom_domain before removal) or state prerequisites, so it falls short of a full 5.

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