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

Annotations already declare destructiveHint=true and idempotentHint=true. The description adds context by explaining the result (number returns to the unassigned registry pool) and the HTTP semantics (DELETE /api/v1/phone-numbers), which is helpful and does not contradict annotations.

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 sentences, the first conveys the core action and result, the second a precise API reference. No filler; front-loaded and efficient.

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 simple two-parameter tool with an output schema and strong annotations, this description covers the purpose, resource, and outcome. It is sufficiently complete for an agent to invoke it correctly.

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%, so both parameters (business_id and phone_number) carry full descriptions in the schema. The tool description adds no extra meaning to them, and with baseline 3, the schema does the work.

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: 'Release a phone number from a business back to the unassigned registry pool.' It also adds the REST mirror, which reinforces the exact action and helps distinguish it from attach_number/buy_number.

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 action itself implies usage: when you need to release a number. But there is no explicit guidance about when not to use it, no mention of alternatives like attach_number or buy_number, and no exclusions or conditions stated.

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