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

Annotations already declare destructiveHint=true, so the bar is lower, yet the description still earns credit by spelling out the concrete consequences: the number stops taking calls and billing/rental ends. The idempotency warning adds behavior the annotations only hint at (idempotentHint=false). It does not address reversibility or whether the number can be recovered.

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?

Two tight sentences with no filler; the destructive effect is front-loaded and the idempotency caveat follows. Every clause carries information an agent needs before calling.

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?

With annotations covering the safety profile and a fully described schema, the description supplies the remaining essentials: what the release does and how retries behave. Only irreversibility and post-release state are left unstated, which is a minor gap for a three-parameter tool with no output schema.

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%, and the schema already documents numberId sourcing from list_numbers and the full idempotencyKey retry semantics, including header precedence. The description restates that meaning rather than adding new detail, so the 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?

The description opens with a specific verb and resource ('Release a phone number') and immediately states the effect ('stops taking calls and its rental stops'), which clearly separates it from the sibling provisioning tool. It lacks an explicit contrast with ringkit_provision_number, so it stops just short of a 5.

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?

It gives clear operational context for when to use this tool and adds concrete retry guidance ('Reuse an idempotencyKey when retrying; without one, each call executes again'). It does not state when not to release or any prerequisite checks, so it is clear but not exhaustive.

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