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 substantial context beyond them: non-ERC-20 input returns 422 uncharged, pricing ($0.003/call via x402 USDC or card key, first 25 free, failed calls free), and an explicit restatement of non-mutation with the caveat that repeats are not free (explaining the idempotentHint=false). It stops short of describing response shape or caching, but for a paid read this is well above the annotation bar.

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?

Purpose is front-loaded, followed by usage routing, input semantics, example, then pricing/safety. Every sentence carries information, though the pricing and 'reads or computes only' sentence is dense enough that it slightly dilutes the core purpose statement.

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?

No output schema exists, yet the description enumerates the returned fields (name, symbol, decimals, total supply) and covers the error case and cost model. An agent has everything needed to call this correctly and interpret the result.

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 token parameter is already documented, which sets a baseline of 3. The description goes further by giving a concrete example address and by stating the failure semantics of the parameter (a non-ERC-20 address returns 422, uncharged), which the schema does not convey.

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 (look up) and resource (ERC-20 token contract on Optimism) and enumerates exactly what is returned: name, symbol, decimals, total supply. It explicitly distinguishes itself from the sibling op_token_balance, so an agent can route between the two without opening either 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 both when-to-use cases ('identify an unknown token address', 'format raw amounts') and names the alternative for a different need ('for a holder's balance use op_token_balance'). This is explicit when/when-not/alternative guidance.

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