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

The description adds genuinely useful context the annotations do not carry: data is read live from the contract, and each successful call costs $0.001 USDC on Base via x402, which is a real behavioral constraint. There is mild tension with readOnlyHint=false and idempotentHint=false for what is described as a live read, though the x402 payment makes the call not strictly side-effect-free, so this is a discrepancy to note rather than a hard contradiction.

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?

Three short sentences, front-loaded with what is returned, then when to use it, then the cost caveat. Every sentence earns its place and nothing is padding.

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?

There is no output schema, so the description correctly enumerates the returned fields itself, and it discloses the payment requirement, which an agent must know before invoking. For a one-parameter read tool this is complete.

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 and it is documented as a 0x ERC-20 contract address. The description adds no format or validation detail beyond that, so the schema does the heavy lifting — 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/resource (read ERC-20 metadata) and enumerates exactly what comes back: name, symbol, decimals and total supply. It also pins the chain (Polygon PoS) and distinguishes itself from the sibling polygon_token_balance, which returns balances rather than metadata.

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 situations for calling it (identifying an unknown token address, formatting raw amounts) which is clear usage context. It stops short of naming an alternative tool or stating when not to use it, so it falls one step below the explicit routing seen in the best definitions.

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