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

The annotations already establish that this is a read-only, idempotent, non-destructive operation. The description adds meaningful behavioral context beyond that: it explains the FX source and date, notes that each item includes official source_url and verified_on, and explicitly says nothing is estimated beyond stated prices. 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 purpose and default scenario are front-loaded, and the clause-heavy content is largely relevant because there is no output schema. However, the description is a single sprawling sentence with nested parentheticals, which makes it harder to parse than necessary.

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?

With 11 parameters, no output schema, and only read-only annotations, the description does substantial work by enumerating the returned cost components, currencies, FX handling, shares, batch/long-prompt details, cache_write_not_stated, and source provenance. It is therefore largely complete for an agent to call and interpret the tool, despite omitting explicit sibling-selection guidance.

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%, so the schema already documents all 11 parameters in detail. The description reinforces the default scenario across several parameters and states that every field can be changed, but it does not add much parameter semantics beyond what the schema provides.

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 computation: monthly AI API cost per bill item for every compared model or a selected provider/model set, broken into input, cache read/write, output, and total. It is easy to distinguish from generic product or energy tools, but it does not name or contrast with relevant siblings such as compare_digital or digital_price_history.

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 supplies a default scenario and notes that every field can be changed, but it gives no explicit guidance on when to choose this tool versus alternatives like compare_digital or digital_price_history. There are also no stated exclusions or prerequisites for use.

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