compare_registrars

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

No annotations are provided, so the description carries the full burden. It discloses return format ('per-registrar rows with buy links'), a cache-dependent failure mode ('notice if no fresh cached pricing exists'), and implicitly the presence of caching. It does not detail rate limits or data freshness guarantees, but for a simple lookup this is reasonably transparent.

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 efficiently cover purpose, use case, exclusion, and return behavior. Every clause adds value and the description is front-loaded with the core action.

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 having only one parameter and no output schema, the description provides sufficient context: what it does, when to use it, what it returns, and an edge-case notice. It is complete for an agent to invoke this tool correctly.

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 already fully describes the single parameter 'tld' with format and leading-dot stripping (100% coverage). The description adds 'given TLD' but no additional parameter details, so the baseline of 3 applies.

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 specific verb and resource: 'Compare what 6 registrars charge for a given TLD' and includes the exact pricing dimensions (first-year, renewal, 3-year total). It explicitly distinguishes itself from check_domain, making the purpose unmistakable.

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 exactly when to use the tool: 'Use for pricing a TLD you already intend to buy' and clearly excludes the availability case with a named alternative: 'this does NOT check whether a specific domain is free (use check_domain for that)'.

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