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

Annotations already declare this tool read-only, idempotent, and non-destructive. The description adds meaningful behavioral context by explaining it is free, provider-neutral, and that it 'does not browse, compare, promote, recommend, price, sell, or link to products, plans, carriers, or connectivity services.' This goes beyond what the annotations alone convey.

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?

Three sentences with no wasted words: the core purpose is first, followed by use cases, then the exclusion/disambiguation, then behavioral boundaries. Every sentence earns its place.

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?

Given that the tool has an output schema, six fully described parameters, and annotations covering safety, the description supplies the remaining needed context: purpose, use cases, exclusions, and what the tool intentionally does not do. Nothing essential is missing.

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%, so the schema already documents all six parameters. The description mentions high-level use cases but does not add parameter-level detail; the schema carries that burden, so the baseline score of 3 is appropriate.

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 names a specific verb ('Creates') and a concrete resource ('a free, provider-neutral mobile-data estimate and readiness checklist for a travel route'). It explicitly distinguishes itself from the sibling tool by stating it is not for pure phone eSIM compatibility questions.

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 description lists clear use cases (trip data budgeting, hotspot planning, offline readiness, connection fallback advice) and gives an explicit alternative for a related but different task: 'Do not use it for a pure phone eSIM compatibility question; use check_esim_device_compatibility instead.'

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