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

It adds real context beyond the annotations: failed/422 calls are uncharged, first 25 free, $0.01/call via x402 USDC or card key. It also reconciles idempotentHint=false by explaining the repeat charge is billing, not state change. The score is held at 3 because the pricing/billing detail crowds out other operational behavior (e.g., multi-token formatting example or caching), and the annotation set already carries the read-only safety profile.

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 well, but the second half strings together pricing, free tier, auth method, and error policy in a single dense paragraph with some redundancy ('an address that is not an ERC-20 contract returns 422, uncharged' vs 'failed calls free'). It is information-dense but not tight; splitting billing into its own sentence would improve scanability.

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 compensates by enumerating all four returned fields and showing an example address. Cost, error behavior, and the balance alternative are all covered, leaving nothing an agent needs to call it correctly.

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 schema already documents token as 'a ticker such as USDC or WETH, or the 0x ERC-20 contract address,' so the description mostly repeats it. The only added semantic value is that a non-ERC-20 address returns 422 uncharged and the worked example address, which is marginal beyond the schema.

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 uses a specific verb ('Look up') with an explicit resource and field list ('name, symbol, decimals and total supply of an ERC-20 token contract on Base'), and it distinguishes itself from base_token_balance by naming that sibling. The agent can tell exactly what this returns versus the ~200 sibling tools.

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 states two concrete use cases ('identify an unknown token address' and 'format raw amounts') and explicitly redirects to base_token_balance for holder balances. That is an explicit when-to-use and when-to-use-something-else, not an inference.

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