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

With no annotations, the description carries the full behavioral burden and delivers: balances are read live, each token is priced from its deepest Uniswap v4 USDC pool, a token with no pool says so, and a failed read is refused before payment (a meaningful no-charge-on-failure guarantee). It also discloses cost ($0.002/call), accepted payment currencies, and the two-phase x402 protocol.

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?

Front-loaded with the tool's output and scope, then progressively adds pricing methodology, failure semantics, and payment mechanics. Every sentence carries information, though the pricing and payment sentences are dense and could be trimmed slightly.

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?

For a paid, unannotated read tool with no output schema, the definition covers cost, payment flow, data freshness, pricing source, and failure handling. The only real gap is that it never contrasts this tool with arc_wallet/arc_wallet_history, leaving the agent to infer selection.

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%, so the baseline is 3, but the description adds real meaning beyond the schema: it clarifies the tokens param's role ('up to 20 tokens you list') and explains the payment param's workflow semantics ('call again with payment' after signing terms), which the schema only describes mechanically. It stops short of illustrating the payload format.

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 states a specific verb and resource combination: what an Arc wallet holds, with a USD value per token, enumerating the covered assets (USDC, EURC, APEX plus up to 20 listed tokens). It implicitly separates itself from arc_wallet/arc_wallet_history by emphasizing live USD valuation, but never names or contrasts those siblings directly.

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 gives an explicit two-step usage pattern for the x402 flow: 'Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`. That is actionable context an agent can't infer from the schema. It does not, however, say when to choose this over arc_wallet for plain balances.

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