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

Annotations already cover safety (readOnlyHint=true, openWorldHint=true), but the description adds a critical behavioral fact: the call costs $0.004 USDC on Base via x402. That payment requirement is exactly the kind of non-obvious trait structured fields don't convey. It doesn't mention failure modes for unpaid calls or rate behavior.

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?

Two short sentences with zero waste, front-loading what the tool returns before the pricing detail. Nothing redundant, though the price sentence could be slightly more informative about the payment flow.

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 does describe the shape of results (token holdings with USD values), which is helpful. However, for a paid tool it omits how the x402 payment is made, what an unpaid call returns, and whether custom token lists change the price — gaps that matter for correct invocation.

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 0%, so the description carries the burden. It does clarify the tokens parameter semantics: default is 'ETH plus major tokens' or 'up to 20 you choose', which matches maxItems=20. The address parameter is left unstated, but its meaning is evident from the name and pattern.

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 and scope: a wallet portfolio snapshot on Base covering ETH plus major tokens with live USD valuation. This clearly separates it from siblings like base_balance or base_erc20_balance (single-asset reads), though no sibling is named 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?

No guidance on when to pick this over base_balance, base_erc20_balance, or base_token — the agent must infer portfolio-level vs single-token intent. The price note hints at a paid path but doesn't say when that cost is worth paying or what happens if payment is absent.

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