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

With no annotations, the description carries the full burden, and it does disclose one real consequence: you stop receiving messages on that number. However, it never states whether the release is irreversible, whether the number can be recovered, whether billing stops, or whether confirmation is required — all critical for a destructive-sounding operation.

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 short sentences, zero filler, with the action front-loaded and the consequence second. Nothing is wasted.

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 release/destructive operation with no annotations and no output schema, the description is too thin: it omits reversibility, cost implications, and how to source the required number_id. An agent could call it but cannot judge the risk of doing so.

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 coverage is 50%: api_key is documented in the schema (including its link to sign_up), but number_id has no description anywhere. The tool description adds no guidance on how to obtain a valid number_id, so the undocumented parameter is left fully unexplained.

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 uses a concrete verb ('give up') and a concrete resource ('a phone number'), so it is immediately distinguishable from get_phone_number or list_phone_numbers. It stops short of naming a sibling or spelling out the release semantics, but the action is unambiguous.

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?

'Give up a phone number you no longer have a use for' implies the when (a number you own and no longer need), but it names no alternatives or prerequisites. An agent must infer that the number must already be provisioned via get_phone_number/list_phone_numbers before calling this.

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