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

Annotations already declare destructiveHint=true, idempotentHint=true and readOnlyHint=false, so the mutation profile is known. The description still earns credit by specifying what is actually lost (the domain stops answering) and what survives (the helpcenter.io address), plus the precondition gate and the exact shape of the return. It does not cover reversibility of the domain record or any rate limiting, so it adds real value but not exhaustive behavior.

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-loaded with the effect, then the gating conditions, then the return value — a sensible order with no filler. The 'Returns: { custom_domain } with no domain' line is slightly compressed in phrasing but justifies itself because no output schema exists.

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, open-world mutation with no output schema, the description supplies everything an agent needs: preconditions, the error path and its resolution, the visible effect, and the return value. Nothing material is left for the agent to infer.

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 agent_key parameter has 100% schema description coverage, including credential handling and secrecy rules, so the schema already does the heavy lifting. The description says nothing additional about the parameter, which matches the baseline of 3 when schema coverage is high.

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 ('Disconnect the help center from its custom domain') and immediately describes the resulting state change: the domain stops answering and the help center falls back to its helpcenter.io address. That consequence framing cleanly separates it from the set_custom_domain and get_custom_domain siblings.

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 an explicit use restriction ('Only when the user asks for it') plus the full prerequisite chain: claimed help center, verified email, active plan. It also names the failure mode (capability_locked) and where the next step can be inspected (helpcenter_get_help_center), so the agent knows both when to call and what to do if it cannot.

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