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

Annotations already declare read-only, idempotent, non-destructive, and closed-world behavior. The description adds genuinely non-redundant context: the ranking comes from the OpenCelliD dataset and is a coverage proxy rather than a speed measurement, which guards against misinterpreting results.

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 sentences: the trigger condition first, then the methodology and its key limitation. No filler, and the most decision-relevant information is front-loaded.

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?

With an output schema present, return values need not be explained. Purpose, trigger, data source, and the coverage-proxy caveat combined with annotations make the definition sufficient to invoke 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 100% with both required parameters documented and exemplified ('City, e.g. Tokyo', 'Country, e.g. Japan'). The description adds no parameter-level detail beyond the schema, so the baseline 3 applies.

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 outcome — ranking mobile operators as 'best' for a given city — and describes the actual ranking basis (observed cell-tower density). This clearly separates it from coverage-checking siblings, but it never names a sibling tool to route against, leaving differentiation implicit.

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 opening clause 'Use when the user asks which mobile network is best in a specific city' is an explicit trigger condition. It gives no when-not guidance or named alternative (e.g., check_coverage, list_country_networks) for adjacent questions.

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