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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so safety is covered. The description adds genuinely new context: the balance is 'live' and matches the Home/Wallet headline, and 'which setups this seat can run' signals seat-scoped permissions rather than account-wide visibility.

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?

A single sentence that front-loads the action and then lists the returned values with no filler. Every clause corresponds to a distinct piece of output an agent would care about.

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 parameters and no output schema, the description carries the return-value burden and does so by enumerating the fields. Minor gaps remain around freshness of the counts and whether the balance is formatted or raw, but nothing needed to call it correctly 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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The description correctly does not waste words on inputs.

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 verb and enumerates the exact payload: plan, live wallet balance, seat count, live eSIM count, and runnable setups. That is far more specific than a generic 'get account' and separates it from siblings like get_usage, get_auto_topup, and list_plans, though it never names an alternative explicitly.

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 only implied: the field list suggests a broad account snapshot and the 'same headline as Home and Wallet' note hints it is the summary view. There is no explicit 'use this when…' or 'for detailed wallet history use list_wallet_activity' routing.

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