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

Annotations already establish that the operation is read-only and idempotentщее. The description adds useful behavioral detail beyond that: results are limited to the cheapest gateways, include both USD and IDR, provide a total count and a cheapest entry, and treat free offers as costing 0. It does not contradict the annotations.

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 with no filler: the first sentence states the core purpose, and the second concisely enumerates the return fields and a key edge case. Each clause earns its place, and the most important information 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?

Given that this is a read-only calculation tool with four fully documented parameters and no nested objects, the description is largely complete: it explains the calculation, the required token inputs, the output fields, and the free-offer behavior. It could slightly expand on empty results or error cases, but no output schema exists and the description already covers the essential response shape.

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 coverage is 100%; every parameter already has a description in the schema, including defaults, bounds, and the model source. The description only paraphrases that input and output tokens are expected and does not add semantic detail beyond the schema. A baseline of 3 is therefore appropriate.

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 operation: computing a monthly bill for a model across gateways based on input/output tokens, and names the returned artifacts (cheapest gateways, totalOffers, cheapest entry). It is specific enough to identify the tool's purpose, though it does not explicitly contrast itself with the sibling `compare_model_prices`, leaving some differentiation to the name and title.

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 'given expected input and output tokens' communicates the main input scenario)Skip. No explicit guidance is given about when to prefer this tool over `compare_model_prices`, `top_free_gateways`, or `list_gateways`, and there are no exclusions. The usage context is implied rather than explicitly stated.

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