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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so the safety profile is covered. The description adds genuine value beyond them by disclosing the response content (yes/no plus nearest served town), which matters because there is no output schema. It says nothing about geocoding failure modes or ambiguity for boundary ZIPs, keeping it below a 5.

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, both earning their place: the question defines scope, the second defines the answer. The core constraint is front-loaded and there is no filler.

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 single-parameter, read-only lookup this is complete: annotations cover safety, the schema covers format, and the description covers scope and return values in the absence of an output schema. An agent has everything needed to call 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 0%, so the description must carry the load; it contributes the 'US' qualifier, which the schema does not state. However, the five-digit format is already enforced by the pattern ^[0-9]{5}$, and the description adds no further meaning about leading zeros, territories, or ZIP-vs-ZIP+4 input.

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 phrases a specific question with a concrete resource and scope: a US ZIP code tested against the North Jersey service area, plus the answer shape (yes/no + nearest served town). That is far more than a restatement of the name. It does not explicitly differentiate itself from get_service_info or request_service, so it stops short of a 5.

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?

Usage is implied rather than stated: an agent can infer this is the eligibility lookup to run before request_service, but the description never says so or names either sibling. No when-not guidance or prerequisites are given, leaving the routing decision to inference.

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