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

With no annotations, the description carries the full behavioral burden, and it does add valuable non-schema context: the x402 cost of 0.002 USDC per call on Base. It never states the read-only nature explicitly, nor what happens for a non-ERC20 or wrong-chain address, which are the realistic failure modes for this 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?

Two sentences, zero filler, with the returned fields front-loaded and the cost disclosure trailing. Nothing repeats the schema or the tool name.

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-param lookup with no output schema, the field enumeration effectively documents the return shape, and the cost model is disclosed. What's missing is error/edge behavior (non-ERC20 contract, unverified token) rather than anything structural.

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?

Single required parameter at 100% schema coverage, so the schema already documents it, including an example address. The description adds only the constraint that the address must be an ERC20 contract on Base — useful but marginal, matching the baseline 3.

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 concrete verb/resource pairing ('Token metadata for an ERC20 contract') and enumerates exactly what is returned: name, symbol, decimals, total supply. The chain is pinned to Base, so the agent knows which network's contract to pass. It doesn't explicitly contrast with the sibling evm_token_balance, but 'metadata' vs. 'balance' makes the split reasonably inferable.

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?

'Use it before formatting any token amount or price' gives a clear triggering condition tied to a downstream need, which is more than most definitions offer. There is no when-not guidance and no sibling is named as an alternative, so it falls short of a 5.

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