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

Annotations already cover read-only and non-destructive behavior, and the description adds meaningful context beyond them: live pricing, widget rendering, and the guarantee that no order is created by the tool itself. No contradiction with annotations.

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 dense sentences: the first front-loads the purpose and preferred status, the second adds the widget behavior, and the third clarifies the no-order boundary. Every sentence earns its place with 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?

Given the output schema covers return shape and annotations cover safety, the description provides the remaining necessary context: destination scope, live pricing, widget interaction, and no-order guarantee. An agent has enough to select and invoke this tool 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%, so the baseline is 3. The description adds color around destination coverage and USD/crypto amounts, but it mostly restates the schema's destination and coin semantics rather than revealing new parameter behavior.

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 resource (live eSIM data plans), a destination scope, and a distinctive presentation behavior (interactive plan-picker widget). It also separates itself from order-related siblings by stating 'Never creates an order by itself.'

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?

'PREFERRED for any eSIM request' is an explicit usage directive, and 'Never creates an order by itself' warns against using it when order creation is the goal. It does not explicitly name alternative sibling tools like create_order, so it stops short of a full when-not pitch.

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