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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds valuable behavioral context: per-mode credit costs and the fact that charges occur only on successful calls. It does not discuss rate limits or error behavior, so it falls short of the highest level.

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 definition is front-loaded with the core purpose, then covers returns, alternatives, and costs in a compact sequence. Every sentence adds decision-relevant information with no filler.

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 only two parameters, no output schema, and clear read-only annotations, the description is complete enough for correct invocation. It explains what each mode returns and what the costs are, so an agent does not need additional return-value documentation.

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 documents both parameters and the mode enum. The description goes beyond that by mapping each mode to its return data and cost, making the enum semantically meaningful rather than just a list of strings.

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 uses a specific verb and resource ('Get comprehensive domain intelligence') and immediately enumerates the mode-specific outputs. It explicitly distinguishes itself from sibling tools by directing business-company questions to companies and registration-name searches to domains.

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 states when to use this tool ('technical facts about a domain') and names the exact alternatives for two adjacent use cases: companies for business facts and domains for finding a registrable name. The mode costs further help an agent choose the right depth.

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