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

The annotations already carry readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds behavioral context beyond that: the operation spans all supported TLDs and registries and returns detailed per-domain results. It doesn't mention rate limits or result structure, but the additive scope and detail-level information earn it slightly above baseline.

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 compact and front-loaded, with the core purpose in the first sentence and a useful alternative in the second. It loses one point for the redundant 'checkKeywordAvailability:' prefix that merely repeats the tool name already known from the context.

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 is sufficient for basic selection and invocation: it states scope, result granularity, and when to use the faster alternative. However, since there is no output schema, the phrase 'detailed per-domain results' is vague about what fields the agent should expect, and it doesn't clarify default behavior when tlds or registries are omitted beyond the implicit 'all supported.'

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?

Schema description coverage is 100%, so the schema fully documents keyword, tlds, and registries. The description adds no parameter-specific syntax or semantics beyond what the schema already provides, making the baseline of 3 appropriate.

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 begins with a specific verb and resource: 'Check keyword availability across all supported TLDs and registries with detailed per-domain results.' It also distinguishes this tool from the summary variant by emphasizing detailed per-domain results, so an agent can identify its unique purpose without opening sibling schemas.

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 explicitly names the alternative tool, checkKeywordAvailabilitySummary, and gives the condition for choosing it: 'when you only need counts; it is faster.' This is clear, actionable routing guidance that leaves little to inference.

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