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

Goes well past the annotations: data is read live from the contract, non-ERC-20 addresses return 422 and are uncharged, pricing is $0.01/call with 25 free calls, and repeated identical calls are still billed (consistent with idempotentHint=false). This is exactly the payment and failure-mode context the annotations cannot express.

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 action and output fields, then usage, then input, then cost. Dense with semicolon chains and pricing detail in the final sentence, but no sentence is pure filler.

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 enumerating the returned fields. Input format, failure semantics, and billing are all covered, so an agent can call this correctly on the first attempt.

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 already 100%, so the description only needs to add value and it does: it clarifies that the same field accepts either a ticker or a 0x address, supplies a worked example, and documents the error behavior for an address form input. It stops short of tie-breaking guidance such as ticker ambiguity across tokens.

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 Avalanche) and explicitly names the sibling it is not (avax_token_balance for holder balances). An agent can distinguish it from the dozens of avax_* siblings and the cross-chain token_info tools without opening 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 two concrete use cases (identify an unknown token address, format raw amounts) and an explicit exclusion routing balance queries to avax_token_balance. The 422-on-non-ERC20 note further tells the agent when this tool is the wrong call.

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