Balances

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered; the description goes further by disclosing the no-wallet error case and a critical cross-field caveat (the `eth` gas field is absent on Arc and must never be added to the USDC balance). It does not cover rate limits or refresh/freshness behavior, so it stops short of a 5.

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, front-loaded with the core read action, followed by the field caveat and the error case. The parenthetical enumeration of the four networks is slightly heavy but genuinely useful since it defines the valid scope; nearly 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?

With no parameters and no output schema, the description carries the burden of explaining the return shape, and it does so reasonably: it names the two balance types, flags the missing `eth` field per chain, and states the error case. Minor gap is freshness/caching and what happens across multiple networks at once.

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 the baseline is 4. The description's field-level discussion (USDC vs `eth` gas balance and their relationship on Arc) concerns returned values rather than inputs, but it does add interpretive value that the empty schema cannot.

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 ('Reads') and resource (USDC and gas-token balances) for the active account, and pins the scope to the active network with named chains. An agent can immediately distinguish this from get_wallet_status or get_history without opening a 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?

Usage is implied by the purpose but never stated as when-to-use or when-not-to-use, and no sibling tool is named as an alternative. The only routing signal is the failure condition ('Errors if there is no wallet'), which is a precondition rather than guidance on choosing this tool.

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