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

Adds substantial behavioral context beyond the readOnly/idempotent/non-destructive annotations: determinism ('no model is involved, so the same keyword always produces the same candidates'), a retry loop ('keeps drawing until it has `count` names free'), and an output-quality guarantee ('what comes back is registrable, not merely plausible'). These are execution traits an agent must know and are absent from the 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?

Purpose is front-loaded in the first clause, followed by execution behavior and then routing. The three sentences are dense but every clause contributes; the only mild redundancy is that the synonym/antonym/realWords/maxWords recap in the final sentence partially re-states the 100%-coverage schema.

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 12-parameter tool with no output schema, this is close to complete: annotations and schema cover safety and parameters, and the description covers purpose, execution cost (retry loop), and result quality. The notable gap is the untold return shape — a bare list of name strings versus objects carrying TLD/availability fields — which a missing output schema would otherwise have supplied.

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 baseline is 3. The description adds real meaning on top: `count` is framed as a guarantee satisfied by continued drawing rather than a mere return limit, and the default blending behavior ('synonyms by default', 'antonyms too') clarifies the effective state of the boolean parameters. Some restatement of realWords/maxWords remains, but the added semantics push it above baseline.

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?

Opens with a specific verb+resource: 'Turn a keyword into brandable name candidates that are free to register.' It states the scope (derived from a keyword, verified as registrable) and is clearly distinct from the sibling set — the closest overlapping sibling, search_domains, is explicitly named, while the generation focus separates it from save/remove/list favorites and username-check tools.

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 closing instruction routes the agent to the one genuinely overlapping sibling: 'Pass anything promising to search_domains for a wider sweep of extensions.' This gives clear workflow context and an explicit alternative condition, though it stops short of a full when-not-to-use or exclusion matrix for the other siblings.

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