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

Adds substantial context beyond the annotations: credit charging on the paid provider (~100-300), the free-provider fallback where organicTraffic/organicKeywords return null and nothing is charged, the 12-hour cache and the deliberate non-caching of empty results. The null-vs-zero semantics and authoritySource labelling rules ('tranco' is a popularity stand-in, not link-graph authority) are exactly the kind of disclosure annotations cannot carry, and readOnlyHint=false is consistent with a billable lookup.

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 and the 'use this first' directive are front-loaded, and nearly every sentence carries distinct, non-redundant operational information (null semantics, billing, caching). It runs long with several stacked caveats, but there is very little pure padding.

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?

With no output schema and read-only-but-billable behaviour, the description carries the full burden and does so: it enumerates the returned metrics, explains null origin per field, states the cost profile, and describes the authority source semantics. An agent has everything needed to call this correctly and interpret the result honestly.

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 already documents domain, projectId, languageCode, locationCode and includeSubdomains, including defaults and fallbacks. The description adds no parameter-level meaning (it discusses organicTraffic, organicKeywords and authoritySource, which are return fields, not inputs), so the baseline of 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 and scope: 'a high-level view of a domain's organic footprint: estimated organic traffic, organic keyword count, and a 0-100 domain authority score.' It also explicitly names the sibling it is not (backlinks/referringDomains vs get_backlinks_overview), so an agent can distinguish it from get_domain_authority_history, get_domain_batch and get_backlinks_overview without opening a 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?

'Use this first for domain research' gives explicit ordering guidance, and it routes the backlink/referring-domain case to get_backlinks_overview. It does not, however, position this against close siblings such as get_domain_batch or get_domain_authority_history, so the coverage is clear-but-not-exhaustive rather than fully explicit.

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