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

Annotations already cover readOnly, idempotent, non-destructive, and open-world, so safety is established. The description adds genuinely new context: that the call is free and that it returns both the USDC balance and the native gas balance, which matters for the stated pre-bridge check use case.

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, each doing distinct work: cost, capability and scope, then usage. The cost note and the action guidance are front-loaded and there is 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?

With an output schema present, the description need not describe return values, and it fully covers cost, chain coverage, and intended use. Nothing an agent needs to invoke this 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?

Schema coverage is 100% and the single address parameter is fully documented with a regex pattern in the schema, so the description has no gap to fill. It adds no format or semantic detail beyond the schema, making the baseline 3 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?

States a specific resource (USDC and native gas balance of an address) with explicit scope (every CCTP chain at once) and even enumerates the 11 chains. An agent can distinguish this from bridge_quote, bridge_routes, or payment_readiness without opening any schema.

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?

"Use it before paying or bridging to see where your money is" gives a clear triggering context, which is exactly the pre-flight check role this tool plays among the bridge/payment siblings. It does not name a specific alternative tool or state when not to use it, so it falls short of a 5.

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