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

With no annotations, the description carries the full burden. It reveals the workflow (check, ask, route), the return format (availability, price in cents), and notes that crypto payment is 'autonomous' while others open a browser. It doesn't mention authentication or error conditions, but for a read-only check tool this is sufficient transparency.

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 description is more verbose than the average tool but every sentence earns its place. It front-loads the purpose, then uses a numbered list and bullet points for workflow steps. The length is justified by the complex decision logic, though it could be slightly tightened.

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?

Despite a single parameter and a rich output schema, the description provides all needed context: it explains when to use it, how to interpret results, how to interact with the user, and which sibling tool to call next. It even includes a conditional recommendation based on MCP configuration. The only minor omission is prerequisites like authentication, but that is likely assumed in the suite.

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 schema has zero description coverage, but the description fully compensates by defining the parameter: 'The full domain name to check (e.g. "coolstartup.com")'. It also explains the return value, making the single parameter's meaning entirely clear.

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 opens with a clear verb and resource: 'Check if a domain is available for purchase and get its price.' It also distinguishes itself from siblings by stating 'Always call this before buying' and listing the buy_domain variants, making its role as a pre-purchase check explicit.

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 provides explicit when-to-use instructions: 'Always call this before buying.' It further details exactly what to ask the user after showing the price and routes to specific sibling tools (buy_domain, buy_domain_crypto, buy_domain_mpp) based on payment method, including a default decision rule for Coinbase MCP.

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