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

Annotations already cover readOnly/destructive, but the description adds material context: pricing ($0.01/call, first 25 free, failed calls free), the 422-uncharged failure mode, and the non-idempotent cost implication ('repeats are not free'). That is behavior an agent cannot infer from the hints.

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 purpose and the sibling redirect, then input format and example. The pricing/billing sentence is dense and slightly tacked on, but every clause 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?

No output schema exists, so the description carries the return burden — and it does, enumerating name, symbol, decimals, and total supply. With the error behavior and cost model also disclosed, 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 ticker-vs-address input is already documented. The description goes beyond it with a concrete example address and the error semantics for a non-contract address, adding real value on top of the schema.

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 name/symbol/decimals/total supply of an ERC-20 contract on Polygon PoS) and returns it is live from the contract. It explicitly distinguishes itself from the sibling polygon_token_balance, so an agent can route without opening any 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 two concrete use cases (identifying an unknown token address, formatting raw amounts) and names the alternative for the other need ('for a holder's balance use polygon_token_balance'). The when-not condition (non-ERC-20 address returns 422) is also spelled out.

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