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

Annotations carry safety hints, but the description goes well beyond them: it discloses error behavior (non-ERC-20 input returns 422 and is uncharged), billing semantics ($0.003/call via x402 USDC or card key, first 25 free, failed calls free), and explicitly justifies the unusual readOnlyHint=false ('not marked read-only because each call is charged'). That explanation resolves what would otherwise be a confusing annotation for a read-only tool.

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 routing, then example, then commercial terms. Every sentence is informative, though the pricing/trial details add length that is tangential to invocation mechanics.

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, but the description enumerates the returned fields (name, symbol, decimals, total supply), documents the error case, and covers cost. An agent can call this correctly and interpret the result without additional resources.

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 single 'token' parameter is already documented, giving a baseline of 3. The description adds a concrete worked example address and the failure mode for non-contract addresses, which is meaningful context the schema does not carry.

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 (name, symbol, decimals, total supply of an ERC-20 contract on Base), including that values come live from the contract. It explicitly distinguishes itself from the closest sibling by routing holder-balance lookups to base_token_balance.

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?

Names two concrete use cases (identifying an unknown token address, formatting raw amounts) and the explicit alternative for balances (base_token_balance). The agent has everything needed to choose between base_token_info, base_token_balance, and base_is_contract without opening a schema.

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