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

With no annotations, the description carries the full behavioral burden. It does disclose that results are returned in both USD and TWD, which is genuine output behavior, but it says nothing about whether live pricing is used, pricing staleness, required auth, or rounding/currency-conversion assumptions.

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?

Two tight sentences: purpose and currency first, then parameter routing. No filler, and the most decision-relevant information (currency of output, which param for which modality) 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 7-parameter estimation tool with no annotations and no output schema, the description covers the main input-routing cases but omits the meaning of cached_tokens and the source/freshness of the pricing data, leaving the agent unable to fully call it correctly for cached-token scenarios.

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 0% with 7 parameters, so the description must compensate, and it does: it explains which inputs correspond to which model type, effectively documenting five of the seven parameters. cached_tokens and the semantics of model are left unexplained, so it is not a full 5.

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 leads with a specific verb and resource, '估算…花費' (estimate … cost), and names the two output currencies (USD and TWD), so the agent knows exactly what is produced. It does not explicitly distinguish itself from the sibling get_ai_api_pricing, which is a pricing lookup rather than a calculator, so it falls short of a 5.

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?

It gives useful input-routing guidance by mapping model modality to the parameter to supply (text→input_tokens/output_tokens, image→images, video→seconds, speech→characters). However, it never states when to use this tool versus siblings like get_ai_api_pricing or get_ai_api_pricing-plus-subscription tools, nor any exclusions or prerequisites.

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