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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds real domain context beyond them: ERC-721 resolves to a single owner while ERC-1155 can have many, which tells the agent what to expect in the result set.

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?

Two tight sentences with the core capability front-loaded and the sibling routing second. No filler or redundancy.

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?

An output schema exists, so return-value explanation is unnecessary, and the description still surfaces the salient output fact (total owner count). Combined with annotation coverage and full schema descriptions, it is nearly complete; only the rationale for the event_types/sort_direction parameters is left unexplained.

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 description coverage is 100%, so the schema already documents chain, contract_address, token_id, limit, cursor, event_types, and sort_direction. The description adds no parameter-level detail, and it notably does not explain why event_types/sort_direction apply to an owners listing. Baseline 3 is appropriate.

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?

The description states a specific verb and resource ('Fetch the wallets holding one OpenSea NFT plus the total owner count') and immediately differentiates scope via the ERC-721 vs ERC-1155 behavior. It also names the sibling tools it is not, so an agent can place it 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?

It explicitly routes the agent to alternatives ('Use opensea_item for NFT details or opensea_item_activity for transfer history'), giving a clear condition for each sibling. It stops short of stating an explicit when-to-use for this tool itself, but the owners scope is unambiguous.

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