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

The readOnlyHint annotation covers the read-only nature, and the description adds that the status is live, requires a connected agent wallet (OAuth or ak_live_ key), and applies only to eSIMs the user owns. This goes beyond the annotation without contradicting it.

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?

The description is five short sentences, each providing a distinct piece of value: what it returns, read-only nature, when to use, where to get the ICCID, and auth requirements. No filler or redundancy.

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 no output schema, the description summarizes return values (live status, data used/remaining, expiration date), identifies the lookup key, and covers prerequisites like wallet connection. This is complete for a simple read-only lookup tool.

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?

The input schema already fully documents the iccid parameter with its source. The description reinforces this by explaining the ICCID is returned by purchase_esim, purchase_phone_plan, or list_orders, adding useful context beyond the schema.

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 clearly states the tool returns live status, remaining/used data, and expiration date for a single eSIM identified by ICCID. This specific verb+resource combination distinguishes it from list_esims (which lists all eSIMs) and purchase_esim.

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?

It explicitly says to use after a purchase or when a user asks how much data is left or whether an eSIM is active. It does not name alternatives or exclusions, but the usage context is clear and actionable.

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