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

Annotations already establish readOnly/idempotent/non-destructive, so the bar is lower; the description adds genuinely non-obvious behavior: row-quota consumption per call and the has_more pagination contract. It does not mention rate limits or result ordering, keeping it below a 5.

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?

Front-loaded with what is searched, then constraints, then return shape; no filler sentences. The return-field enumeration is long but earns its place because there is no output 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 27-parameter tool with no output schema, the description covers the filter precondition, pagination signal, row-quota cost, and the shape of each result row. Minor gaps remain (no default sort, no note on how page interacts with page_size limits per plan).

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 coverage is 100%, so the baseline is 3, but the description adds meaning the schema lacks: which filters qualify as 'selective' (keyword of 2+ chars, tlds, listingTypes, price range, min* above 0) and what each returned row contains. That grouping is real added value beyond per-parameter 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?

States a specific verb and resource ('search UpSnatch's catalog of expired, dropped, pending-delete, auction and marketplace domains') and the filter dimensions (keyword, SEO metrics). This is clearly distinguishable from the single-record sibling get_domain without opening either schema.

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?

Explicitly states the precondition that at least one selective filter is required and enumerates what counts as selective, which prevents empty-catalog scans. It does not explicitly contrast with get_domain (the only sibling), so it falls short of full when/when-not routing.

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