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

Annotations already declare readOnlyHint and openWorldHint, but the description adds material context beyond them: cost ('Free'), custody guarantees ('Tollkit never holds anyone's funds or keys'), and the fact that it moves nothing. It also previews the return payload. Missing only deeper operational detail like failure modes when the address is malformed.

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?

Well front-loaded and organized into labeled sections (When to use / Use instead / Parameters / Returns). Slightly wasteful: 'Free.' appears twice and the return payload is described in the opening sentence and again under 'Returns'.

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?

No output schema exists, and the description compensates by stating what is returned (the USDC balance and whether it falls below low_below). Combined with full parameter coverage and the safety profile, an agent has everything needed to invoke and interpret this tool.

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 description coverage is 100%, so all three parameters are already documented in the schema, including defaults and the enum. The description restates them (address 'the wallet you pay from', network default base, low_below default 1) with only slight added framing, so the baseline of 3 applies.

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 resource with scope: 'Check how much USDC is left in your own wallet on Base.' It explicitly contrasts itself with the sibling 'wallet_balance for any wallet, chain or token,' so an agent can route correctly without opening either 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?

Provides an explicit 'When to use' trigger (you pay for tools from a wallet and want to know if it's running low) and an explicit 'Use instead' alternative (wallet_balance) with the condition that selects it. Nothing is left to inference.

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