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

With no annotations provided, the description carries the burden of behavior disclosure and does a solid job: it says the call is a preview, free, and shows constraint effects such as discounts and surge pricing. It does not mention authentication needs or side-effect absence explicitly, but 'Preview' strongly implies a non-mutating read-like operation, and the free disclosure is valuable.

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 compact and well-structured: the core purpose is front-loaded, the second sentence explains what the output covers, and the third gives a key cost fact. Every sentence adds useful information with no repetition or filler.

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 is adequate for a simple cost-preview operation, especially with an output schema available, and it conveys the most important non-obvious context ('Free — no credits required'). However, it lacks guidance about when to use this tool versus many similar 'check' siblings, and partial parameter coverage leaves some ambiguity for an agent planning a correct invocation.

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 description provides no parameter-level guidance, and schema description coverage is only 50%: npub and dpop_token are undocumented in both the schema and description. The description's mention of constraint effects loosely relates to tool_kwargs for ad valorem/categorical pricing, but it does not compensate for the undocumented 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 clearly states a specific action ('Preview the effective cost of a tool call') and identifies the resource ('a tool call'), with examples of what it shows (base cost, discounts, surge pricing). It is distinguishable from most siblings by focusing on cost preview rather than balances, payments, or stock, though it does not explicitly name or contrast any sibling.

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 phrase 'Preview the effective cost of a tool call' implies the tool is used before making a call to assess cost, and 'Free — no credits required' gives a useful usage condition. However, there is no explicit guidance on when to prefer this over related tools like check_balance, check_payment, or get_pricing_model, nor any exclusions mentioned.

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