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

The description discloses key behavioral traits: no fees for instant fills, delivery to cargo or storage when full, auto_list behavior with 1% listing fee (varying by station), and acceptance of item names. With only readOnlyHint:false in annotations, the description carries the burden and covers important side effects (fees, delivery). It does not mention return values or failure modes, but is otherwise transparent.

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?

The description is a single, information-dense sentence that leads with the core purpose. It uses parentheticals to pack detail without rambling, though the delivery/fee clauses make it slightly dense. No wasted words, but it could be split for readability.

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?

The description covers the essential context for a buy tool with 5 parameters and no output schema: market price, instant-fill fee waiver, delivery default, auto_list option with fee implications, and accepted item input forms. It omits specifics like response format or error conditions, but given the tool's straightforward buy action and the schema's parameter descriptions, it is reasonably complete.

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?

Although schema covers 100% of parameters, the description adds meaning by clarifying that item_id accepts either an ID or a human-readable name (e.g., 'Iron Ore'), extending the schema's 'ID of the item' with examples. It also elaborates on auto_list fee variations ('1% default, higher at pirate strongholds') beyond the schema's flat '1% listing fee applies.' This adds value.

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 clearly states the tool's function with a specific verb and resource: 'Buy items at market price from the station exchange.' It distinguishes from sibling buy tools (e.g., buy_ship_license, buy_listed_ship) by specifying 'items' and 'station exchange.' It also notes accepted input formats ('item_id or item name'), reinforcing its scope.

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?

The description provides context on when to use the tool (buying at market price) and internal options (deliver_to, auto_list), but does not explicitly contrast with sibling tools like create_buy_order or cancel_order. It mentions when to use deliver_to=storage and auto_list=true, giving some situational guidance, but lacks explicit exclusions or alternative tool names.

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