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

Annotations already declare readOnlyHint=true, destructiveHint=false and idempotentHint=false. The description adds real value beyond that: pricing ($0.01/call, first 25 free, failed calls free), the 422 uncharged failure mode, and confirmation that calls are billed so repeats are not free — consistent with idempotentHint=false. However, it does not describe the return shape (e.g. how decimals/supply are formatted) or ticker-resolution behavior, which limits it to solid-but-not-rich disclosure.

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 the core purpose and the sibling routing, then supporting detail. It is somewhat dense with pricing/billing sentences that could be trimmed, but each sentence carries actionable 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?

There is no output schema, and the description compensates by naming exactly what is returned (name, symbol, decimals, total supply). Combined with the input clarification, failure mode, and billing context, an agent has everything needed 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%, so the baseline is 3, but the description adds meaning beyond the schema: it clarifies that a ticker or a 0x address is accepted, supplies a concrete example address, and explains the rejection behavior for non-ERC-20 addresses. That extra context on the single parameter's accepted forms justifies a 4.

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: look up name, symbol, decimals and total supply of an ERC-20 contract on Optimism, live from chain. It explicitly routes away from the nearest sibling ('for a holder's balance use op_token_balance'), so an agent can distinguish op_token_info from op_token_balance and the other op_* tools without reading a schema.

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 concrete use cases ('identify an unknown token address or to format raw amounts') and an explicit exclusion with the named alternative for holder balances. It also states what happens on invalid input (non-ERC-20 address returns 422, uncharged), covering when-not conditions.

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