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

Goes well beyond the annotations by disclosing error semantics (404 for missing contract, 422 for non-ERC-721, both uncharged), the pricing model ($0.01/call, 25 free, failed calls free), and that repeat calls are charged — which explains why idempotentHint is false. It also confirms read-only/no-mutation, consistent with readOnlyHint=true and destructiveHint=false.

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 and the sibling routing are front-loaded in the first two sentences, and the error/pricing details are genuinely decision-relevant. It is dense but slightly sprawling, with payment mechanics taking up roughly half the text.

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?

With no output schema, the description still says what comes back (balance plus collection name and symbol). Combined with error codes, cost model, and read-only confirmation, an agent has everything needed to call this correctly and interpret failures.

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%, with both parameters already documented as '0x wallet address' and '0x ERC-721 collection contract address'. The description only restates that both inputs are 0x addresses, adding no format, validation, or edge-case detail beyond the schema, so baseline 3 applies.

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 — NFT balance of one ERC-721 collection for a wallet on Base — and even names the underlying call (balanceOf). It explicitly separates itself from base_nft_owner ('for who holds one token id use base_nft_owner'), so an agent can pick between the two siblings 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 concrete use cases (check a holder before a token-gated action, verify a wallet still holds a collection) and an explicit exclusion routing to base_nft_owner. When-to-use, when-not-to-use, and the alternative are all present.

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