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

Annotations already cover safety (readOnlyHint, destructiveHint=false), so the description focuses on what they cannot express: the cost model ($0.01/call, first 25 free, failed calls free), the 422/unbilled failure mode, and the fact that repeats are charged. That last point directly explains why idempotentHint is false for an otherwise pure read, which is genuinely useful context.

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 what it returns, then when to use it, then the input format and example, then the commercial terms — a sensible order with no filler sentences. The payment/pricing sentences are dense and could be trimmed slightly, but each carries decision-relevant information.

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 one required parameter and no output schema, the description supplies the return fields, the accepted input forms, an example, the failure mode, and the billing behavior. Nothing an agent needs in order to call this correctly and interpret the result is missing.

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 says the token may be a ticker like USDC/WETH or a 0x contract address, so the description largely restates it. The added value is only the worked example address and the validation behavior for non-ERC-20 input, which is modest beyond what the schema provides.

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 ('look up the name, symbol, decimals and total supply of an ERC-20 token contract on Polygon PoS') and names the exact fields returned, so the agent knows what comes back without opening a schema. It is also explicitly distinguished from the closest sibling by pointing at polygon_token_balance for holder balances.

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?

Gives two concrete use cases ('identify an unknown token address', 'format raw amounts') and names the alternative tool plus the condition that selects it. It also states what happens when the input is not an ERC-20 contract (422, uncharged), which removes the main ambiguity an agent could hit.

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