Can I buy? (free) — wallet, balance, prices

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It explicitly states 'never spends anything,' which is a strong safety guarantee, and outlines the specific information reported (wallet address, USDC balance, tier costs). This provides clear expectations about side effects and return content.

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 long and highly efficient. The first sentence states the core purpose (checking affordability), the second adds usage guidance and safety context. Every word contributes value; no filler or redundant information.

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?

Given that the tool has no parameters and no output schema, the description still manages to be complete: it states what is checked, what is reported, when to use it, and the key behavioral guarantee. No critical information is missing for an agent to use it correctly.

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?

The tool has zero parameters, so schema coverage is trivially 100%. The description doesn't need to explain parameter semantics and doesn't waste space doing so. Baseline is 4 for zero-parameter tools, and the description adds no unnecessary parameter detail.

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 starts with a specific verb 'Check' and identifies the resource (buying key affordability for a watch). It goes beyond a bare restatement by naming the exact outputs (wallet address, USDC balance, tier costs) and explicitly distinguishes itself from sibling tools by referencing create_watch. This fully clarifies 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 gives explicit usage guidance with 'Call this before create_watch; it never spends anything.' This tells the agent exactly when to invoke it (as a precondition to create_watch) and provides a key exclusion (never spends), clearly differentiating it from mutation tools.

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