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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds genuinely useful behavior beyond that: 'Free, cached data,' which tells the agent the results may be stale and involve no billing/rate-limit risk, and it names the output payload, which matters since no output schema exists.

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 front-loaded sentence — resource first, then the payload inventory — with no filler. 'Free, cached data' carries real information, though the enumerated list is dense and one item ('with explanation') is vague enough to add little.

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 two-parameter, read-only, open-world query tool whose annotations carry the safety profile and whose schema is fully documented, the description covers purpose and output contents adequately. The remaining gap is routing versus the backlink- and keyword-specific siblings, which is minor here.

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 both parameters (domain, country enum with default 'us') are already documented with examples and an enum list. The description adds nothing about the domain format or the country/market parameter, so the baseline 3 applies.

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 resource (SEO snapshot of any website) and enumerates exactly what the snapshot contains: Authority score, organic traffic, ranking keywords, competitors, and backlink summary. This content list implicitly separates it from narrower siblings like backlinks_summary and keyword_overview, though it never names them outright.

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 implied by 'SEO snapshot of any website' — the agent can infer this is the general entry point — but there is no explicit when-to-use, when-not-to-use, or alternative routing (e.g., use domain_history for trends, backlinks_summary for deeper link data). Overlap with backlinks_summary is left for the agent to resolve.

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