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

Annotations already declare readOnlyHint=false, openWorldHint=true, idempotentHint=false, and destructiveHint=false. The description adds substantial operational context beyond those annotations: OAuth or live key required, no test mode, one prepaid wash per distinct valid number, free invalid numbers, and refunds for unanswered register checks.

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?

Four short sentences, front-loaded with purpose, followed by authentication, billing, and endpoint details. Each sentence carries useful information without repetition or 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?

The description adequately covers authentication, cost, refunds, and the equivalent endpoint for a one-parameter tool with annotations. It stops short of explaining what each washed number returns and does not explicitly differentiate from sibling tools, which are modest gaps given the lack of an output schema.

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?

There is only one parameter, and schema description coverage is 100%, including the 500-number limit and an example format. The description adds the billing-relevant idea of a distinct valid number but does not need to expand further on parameter syntax.

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?

States a specific verb and resource: washing Australian phone numbers against the Do Not Call Register, with the equivalent endpoint. It is clear what the tool does, but it does not explicitly differentiate itself from siblings such as screen_numbers or check_dead_numbers.

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?

The description gives prerequisites and constraints such as needing a live account and the absence of a test mode, plus billing behavior. However, it does not explicitly state when to choose this tool over screen_numbers or check_dead_numbers, so usage is only implied.

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