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

Annotations already establish read-only, idempotent, non-destructive, open-world behavior, so the description's added value is the billing rule ('billed per started block of 10 domains that have data') and the data-source scope (Google, one country). It does not cover throttling, partial-data handling, or whether domains without data still consume the block.

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?

A single dense sentence with zero filler, front-loaded with the batch limit and payload scope. The colon-separated metric list is slightly run-on but every item earns its place because it defines the payload.

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 read-only aggregate lookup with no output schema, the description supplies the metric set, billing model, and geographic scoping needed to call it correctly. The remaining gap is input formatting of domain strings and behavior on domains with no data.

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?

Country and language are already documented in the schema (67% coverage); the description usefully restates the 100-domain cap and the 'one country' scoping. However, the undocumented 'domains' array remains ambiguous in both places — it does not say whether entries should be bare domains or full URLs, or whether subdomains are accepted.

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 names a specific resource (domain-level SEO overview) and enumerates exactly which metrics come back: organic traffic, ranking keywords, paid keywords, domain rank, backlinks, referring domains, spam score, first seen. That makes it distinguishable from narrow siblings like backlinks or ranked_keywords, though it never names an alternative explicitly.

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?

Usage is only implied: the aggregate metric list plus the 'up to 100 domains' batching hint at bulk overview lookups, while the siblings (backlinks, ranked_keywords, keyword_metrics) suggest the detailed single-metric alternatives but are never referenced. There is no explicit when-to-use / when-not-to-use statement or prerequisite.

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