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 genuinely useful behavior beyond that: the returned field set (price, quantity, validity, marketplace, maker wallet) and the empty-list-instead-of-404 edge case, which prevents an agent from misinterpreting an empty result as a failure.

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 tightly written sentences with the core operation front-loaded and the routing/edge-case note following. No filler, every clause earns its place.

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 an output schema present, return-value detail needn't live in the description, and the alternatives plus empty-list caveat cover the main ambiguities for a read-only item-lookup tool. Minor gap: no mention of pagination behavior (limit/cursor) or the event_types param, though the schema carries those.

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 all seven parameters. The description only echoes the three required identifying params and adds no format or syntax detail beyond the schema, making baseline 3 the correct score.

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 ('Fetch') and resource ('standing OpenSea sell-order records for one NFT'), plus the exact identifying triple (chain, contract, token_id). It clearly distinguishes itself from the named siblings opensea_item_offers and opensea_item_activity.

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?

Explicitly routes the agent to alternatives: 'use opensea_item_offers or opensea_item_activity for offers and events,' and clarifies that missing listings yield an empty list rather than an error. It doesn't spell out every when-not case, but the sibling routing is clear and actionable.

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