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

Annotations already cover safety (readOnly, idempotent, non-destructive, openWorld). The description adds genuine behavioral context beyond them: results are ephemeral offers that expire, and the exact returned offer must be used when claiming. It omits result-count limits and whether repeated searches return different offers.

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: the core action first, then the critical caveat about offer expiry. Every clause carries information an agent needs.

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?

An output schema exists, so return structure needn't be explained. For a two-parameter search the description is nearly complete; the only gap is not hinting at result volume or whether pagination/limits apply.

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 0%, but the two parameters are self-explanatory (country enum US/CA, 3-digit area_code pattern) and the description confirms the US-or-Canadian and area-code semantics. It adds no format or constraint detail beyond that, so baseline 3 is right.

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 (search) and resource (currently available US/CA numbers) with the key scoping qualifier 'available', which implicitly separates it from list_phone_numbers/list_numbers (owned numbers). It stops short of naming any sibling explicitly, so an agent must infer that available-for-purchase differs from inventory listing.

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?

'Claim an exact returned offer' points to claim_phone_number as the follow-up action, and 'offers expire' implies time pressure, but the description never states when to prefer this over list_phone_numbers or get_phone_number, nor any exclusions.

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