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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so the safety profile is covered. The description adds value beyond that by noting the as-of date (data currency), explaining that it teaches how to read the `billing` receipt on htag tool results, and pointing to the mirrored resource. No contradictory claims.

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?

Front-loaded with what the card contains, then the usage formula, then the resource mirror — a logical order. The tier/field enumeration is dense but each item carries real information, so little could be cut without loss.

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?

A zero-parameter read with an output schema, so return shape needn't be restated, yet the description still enumerates the fields an agent would want. Nothing needed to call it correctly is missing.

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 tool takes zero parameters, so the baseline is 4. The description correctly implies no input is needed by framing the call as a direct lookup of a static rate card.

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 states a specific resource and its exact payload: AUD per unit for each tier (Reference, Standard, Enhanced, Premium, Restricted) and each monthly volume band, plus multipliers, free allowance and an as-of date. That level of specificity makes it unmistakable against the sibling tools, which are all documentation/registry listers (get_guide, list_api_endpoints, etc.).

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 a concrete use case with the formula: 'Use it to estimate a call before making it: units x rate x plan multiplier.' It also reveals an alternative access path (the pricing://rate-card resource). What it lacks is an explicit when-not or a named tool alternative, so it sits just below the top.

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