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

The description goes beyond annotations by detailing financial side effects: debits balance, credits seller minus rake, records transaction, and returns the reasoning_graph. It also specifies the API key and balance requirement. This adds significant context not present in the annotations alone.

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 two sentences, both information-dense. The first sentence covers the action and effects, the second covers prerequisites. No redundant or filler content, making it appropriately sized and front-loaded.

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?

For a purchase transaction, the description explains the financial flow, the returned payload, and required credentials. With an output schema present, it doesn't need to detail return values. The combination of annotations and description gives a complete picture for the agent.

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% with each parameter already described. The tool description does not elaborate further on parameter semantics. Per the rubric, high schema coverage yields a baseline of 3, and there is no additional value in the description regarding parameters.

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 opens with a specific verb and resource: 'Buy a listed mint.' It clearly differentiates from sibling tools like fillin_market_search (search) and fillin_mint (likely listing). It also enumerates the transaction flow, leaving no ambiguity about what the tool does.

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 clearly implies usage when a user wants to purchase a listed mint, and notes prerequisites (FILLIN_API_KEY, sufficient balance). It does not explicitly name alternative tools or exclusions, but the context is unambiguous for a buy operation, so it earns a 4 rather than a 5.

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