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

Annotations already declare this is a read-only, closed-world, non-destructive operation, so the description does not need to restate safety. It adds real behavioral context by stressing that the values are 'live' and current and by listing the breadth of what is returned, though it says nothing about authentication, rate limits, or currency/period conventions.

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 sentences, front-loaded with the resource and its contents, then the directive on when to use it. The long enumeration is all substantive coverage information rather than filler, and no sentence is redundant.

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 zero parameters, an output schema present to describe return values, and annotations covering the safety profile, the description carries the remaining burden well: it establishes freshness, scope, and the substitution rule against memory or the knowledge base. Nothing an agent needs in order 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 there is nothing for the description to disambiguate; the baseline of 4 applies. The enumeration of price categories does at least tell the agent what dimensions of data exist even though no arguments select among them.

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 the resource specifically ('FastCAC's own current prices') and enumerates exactly what is covered: business name registration for both personal and agent workspaces, Business Pro, annual returns split into CAC's fee and FastCAC's fee, credit packs, NIN tools, and the developer API. An agent knows precisely the scope of this price catalog without opening the schema.

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 explicit when-to-use guidance ('any question about what FastCAC charges, every time') and explicitly names the wrong sources to avoid — memory, a page, the knowledge base. It does not name the closest sibling, calculate_cac_fees, so an agent asking about a specific fee scenario gets no routing signal between the reference price list and the calculator.

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