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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description goes further by disclosing the data window (since 2018), sampling granularity (one point per quarter), and derived fields (gained/lost/net over 12 months plus trend) — substantial behavioral context beyond the annotations, though nothing on freshness/latency.

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?

Two tight sentences: the first defines the data and its resolution, the second gives the interpretive use. Nothing redundant, and the most decision-relevant facts (metric, coverage, granularity) are front-loaded.

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, the description carries the burden of explaining return content, and it does: history depth, point cadence, the headline metric, and the 12-month gained/lost/net summary. For a single-parameter read tool with annotations, nothing needed for correct invocation 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?

Only one parameter with 100% schema description coverage (including an 'e.g. example.com' example), so the schema does the heavy lifting. The description adds no format, normalization, or subdomain handling detail, which is the baseline-3 outcome when coverage is high.

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 metric (count of websites linking to a domain) and its temporal shape (multi-year history since 2018, quarterly points), which cleanly distinguishes it from siblings like referring_domains and backlinks_summary that report current snapshots. The verb+resource pair is unambiguous.

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?

The closing clause 'Use to see if a site is growing or losing authority' gives an implied use case, but there is no explicit when-not guidance and no alternative tool named (e.g., use referring_domains for the current list). Adequate but leaves routing to inference.

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