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

Annotations already declare readOnly, idempotent and a closed-world scope, so safety is covered. The description adds the return behavior (yes/no plus nearest served town), which is meaningful context given no output schema exists.

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, front-loaded with the core question, followed by the answer shape. Zero wasted words.

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 one-parameter boolean lookup with no output schema, the description supplies both purpose and return shape, which is nearly everything an agent needs. Edge-case behavior (invalid or out-of-country ZIPs) is the only omission.

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 0% for the single parameter, so the description must carry the load: it identifies the input as a US ZIP code, complementing the schema's 5-digit pattern. It does not clarify handling of non-US or malformed codes.

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 states a specific check: whether a US ZIP code falls inside the Las Vegas service area, which separates it from get_service_info and request_service by intent. It lacks an explicit pointer to those siblings, but the verb+resource 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?

The question framing implies this is a pre-qualification check before requesting service, but the description never states when to prefer it over get_service_info or request_service, nor when-not to use it. Usage is inferable rather than stated.

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