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

Annotations cover the safety profile (readOnly, idempotent, openWorld), and the description adds rich behavior beyond them: which fields are ALWAYS null (organicTraffic, organicKeywords, backlinks, referringDomains) and why, the meaning of organicUnavailableReason and authorityUnavailableReason, and that malformed entries are dropped and counted rather than failing the call. This is exactly the costly-to-discover context the description should carry.

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?

It is front-loaded and mostly earns its place, but the middle clause ('since fanning that out across many domains in one call is a materially bigger paid-provider commitment than anything else this codebase does in one request') is verbose internal rationale that an agent does not need to invoke the tool correctly. The valuable null-field and reason-code facts are buried within this long run-on.

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 batch read tool with no output schema, the description supplies the otherwise-invisible response contract — always-null fields, once-per-response reason flags, skippedInvalid counting, and the authority-failed-vs-unranked distinction. Nothing an agent needs to interpret results correctly is missing.

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 baseline is 3, but the description adds meaning: it explains that malformed entries are dropped into skippedInvalid (corroborating the domains param semantics) and highlights the includeSubdomains default differing from get_domain_overview. It adds a bit beyond the schema without fully re-documenting all params.

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 states a specific verb and resource ('Domain batch analysis: one authority row per domain, up to 100 at once') and explicitly distinguishes itself from the sibling get_domain_overview by contrasting cost ('FREE — no paid provider call') and mode (batch vs single). An agent can immediately tell what this tool does and how it differs.

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?

It gives explicit routing: use this for batch authority rows across many domains, use get_domain_overview for organic figures on one domain at a time. The when-to-use and the alternative are both named directly.

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