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

Beyond the read-only/idempotent annotations, the description discloses genuinely important behavior: the 18-decimal fallback assumption and the fact that it is marked as assumed, the found:false response for non-tokens, and the full payment model ($0.002/call over x402, prepaid x-credit-token header, 1 free call/day, no API key). These are the details an agent needs before invoking and budgeting the call.

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?

The core purpose and the decimals caveat are front-loaded before the payment logistics, and every sentence carries information. It runs slightly long, with the pricing/header sentence being the most verbose element, but nothing is redundant filler.

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 one-parameter, read-only tool with an output schema already defining the return shape, the description covers everything an agent needs: scope, decimal-handling behavior, non-token behavior, and cost/access requirements. No material gap remains.

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% for the single 'token' parameter, so the schema already carries the semantics. The description only restates 'Required input: token' without adding format, chain, or address-type nuance, which is the expected baseline when the schema does the work.

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 names a specific on-chain value (totalSupply) scoped to 'any Base token' and states what is returned (raw value scaled by decimals, plus name and symbol). This is far more precise than a tautology, but it never names a sibling such as token_info, b20_supply, or supply_inflation to disambiguate the choice.

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 through edge-case handling (non-token addresses return found:false, missing decimals assume 18) rather than explicit 'use this when / not when' guidance. No alternative tool is named, so an agent must infer when token_supply is the right call versus token_info or b20_supply.

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