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

With no annotations, the description carries full burden for behavioral disclosure. It lists what is returned (registration, cost, renewal, provenance) and implies a read-only operation via 'fetch', but it does not explicitly state that no mutations occur, nor does it mention error conditions or input validation. The information is useful but not comprehensive; a clear 'does not modify anything' would have raised this score.

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 two succinct sentences: the first enumerates the returned data types, the second gives a concrete usage example. It is front-loaded with the core value proposition, contains no redundant phrases, and every sentence earns its place.

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?

For a single-parameter tool with no output schema, the description adequately explains how to call it (id) and what to expect in return. It does not cover potential limits, errors, or currency specifics, but given the simplicity and the fact that the returned data categories are listed, it is sufficient for an agent to invoke correctly. Slight gap in not mentioning any prerequisites or restrictions, but not critical.

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 already provides 100% coverage with the description 'A domain name.' The tool description adds an example ('atlas.io') and clarifies the id should be a domain name, which is slightly more helpful than the schema alone. However, since schema coverage is complete, the baseline 3 applies and the added example is marginal but not transformative.

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 fetches comprehensive information about a single domain, listing specific data points (registration status, cost to claim, renewal cost, and provenance). This distinguishes it from siblings like quote_domain (pricing only) or audit_domain (history) by emphasizing the complete profile. The verb 'fetch' and resource 'domain' are explicit, and the example clarifies the input.

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 implies use for retrieving all available data on one domain but does not explicitly contrast with alternatives or state when not to use it. No mention of sibling tools for narrower queries, leaving selection somewhat to inference. It provides clear context (single domain lookup) but no exclusions or comparisons, so it's adequate but not directive.

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