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

With no annotations provided, the description must bear the burden of behavioral disclosure. It states the tool 'returns cost per use and break-even use count', implying a read-only compute operation, but does not explicitly mention that it has no side effects, requires no authentication, or is idempotent. The information is adequate but minimal.

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 exceptionally concise: three sentences that efficiently convey purpose, usage context, inputs, and outputs. Every sentence adds value, and the most critical information ('Compute the cost-per-use') is 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 simple tool with two parameters and a clear output, the description is complete. It covers what the tool does, when to use it, the inputs (albeit with slight ambiguity), and the outputs (cost per use and break-even use count). The reference to related tools via 'list_bundles' adds useful context.

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 clear descriptions for both parameters ('Item purchase price' and 'Expected number of uses'). The description adds 'Inputs: purchase price, expected uses or years', which aligns mostly but introduces the confusing 'or years' option not reflected in the schema. The added value beyond the schema is marginal.

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 it computes cost-per-use for evaluating purchase value, with specific use case for durable goods or subscriptions. However, the phrase 'expected uses or years' is ambiguous because the schema only includes 'expected_uses' as a number, potentially confusing agents about whether 'years' is a valid input.

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 explicit context: 'Use for buying decisions on durable goods or subscriptions.' It also references 'list_bundles' for related calculators, but it does not specify when not to use this tool or name alternative tools among the many siblings (e.g., calculate_break_even), which would enhance guidance.

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