compare_registrars

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It describes what the tool returns (pricing comparison and recommendation) and the comparison criteria (first year price, renewal price, overall recommendation), but it doesn't mention potential limitations like rate limits, authentication requirements, or what happens with invalid inputs. The example adds some context but doesn't fully compensate for the lack of annotations.

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 well-structured and appropriately sized. The first sentence states the core purpose, followed by bullet points detailing what it checks, a sentence about returns, and a concrete example. Every sentence adds value without redundancy, and it's front-loaded with the main functionality.

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?

Given the tool's moderate complexity (3 parameters, no output schema, no annotations), the description is adequate but has gaps. It explains the purpose and returns but doesn't cover error cases, output format details, or behavioral constraints. Without annotations or output schema, the agent lacks complete guidance on what to expect beyond the basic comparison promise.

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 input schema has 100% description coverage, providing clear documentation for all three parameters. The description doesn't add any parameter-specific information beyond what's in the schema, so it meets the baseline of 3. The example shows parameter usage but doesn't explain semantics beyond the schema descriptions.

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 clearly states the tool's purpose with specific verbs ('compare domain pricing') and resources ('across multiple registrars'), and it distinguishes from siblings by focusing on price comparison rather than availability checking (search_domain), bulk operations (bulk_search), or domain suggestion (suggest_domains). The example reinforces the specific comparison action.

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 provides clear context for when to use this tool (to compare pricing for a specific domain across registrars), but it doesn't explicitly state when not to use it or mention alternatives among the sibling tools. The example implies it's for single-domain comparisons, but there's no explicit exclusion for bulk operations or other use cases.

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