release_phone_number

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

With no annotations provided, the description carries the full burden. It clearly discloses the irreversible nature ('returned to the pool'), the financial implication ('No credit refund'), and the data retention behavior ('Message history is retained'). It stops short of explicitly stating 'this cannot be undone,' but the implications are strong.

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 compact and front-loaded. The first line gives a precise summary, followed by two short sentences of behavioral impact, and a clear Args section. Every sentence adds value; there is no fluff.

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?

Given the tool's simplicity (one parameter, no nested objects) and the presence of an output schema, the description covers all essential aspects: the action, the consequences, and the parameter source. It does not need to describe return values because the output schema exists.

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 only parameter, phone_number_id, is described as coming from list_phone_numbers, providing valuable provenance that the schema lacks. This is exactly the kind of extra meaning that helps the agent select and populate the parameter correctly.

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 'Release a provisioned phone number' – a specific verb and resource that clearly distinguishes it from provisioning, updating, or listing numbers. It is immediately obvious what the tool does and how it differs from 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?

The description explains the consequences (returned to pool, no refund, history retained), which implicitly clarifies when this tool is appropriate – when you want to permanently give up a number without compensation. However, it does not explicitly name alternative tools or state when NOT to use it.

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