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

Goes well beyond the annotations: it names the 404 (missing contract) and 422 (nonexistent token) failure modes and states that failures are uncharged. It also explains the pricing model ($0.01/call, first 25 free, repeats charged) which is the real reason idempotentHint is false. The only gap is that it doesn't describe the response shape in detail, though it does name the returned fields.

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 definition, then use cases, alternatives, error codes, example, and pricing in a logical order. It is dense but every sentence carries operational information; the pricing tail is slightly long for a single-call lookup tool but is genuinely relevant to repeat-call decisions.

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 names the returned values (owner, collection name, symbol) and covers error semantics, cost, and side-effect profile. An agent has everything needed to call it correctly and interpret the outcome.

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 baseline is 3, but the description adds real meaning: the contract must be an ERC-721 collection (not any token contract), the tokenId identifies one specific token, and a concrete worked example (0x3d79…D95A, tokenId=1) shows the expected format. It does not address the schema's odd allowance of boolean tokenId, but otherwise it complements the schema well.

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 resource and operation: the wallet that currently holds a given ERC-721 token id (ownerOf), returned alongside the collection name and symbol. It explicitly distinguishes itself from celo_nft_balance and celo_nft_metadata by name, so an agent can pick the right sibling 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 concrete use cases (verifying a holder before a trade, mint gate, airdrop) and routes the agent to the two alternative tools for the count and metadata questions. Nothing is left to inference about when this tool is the correct choice.

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