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

Annotations declare read-only/safe; the description adds crucial behavioral context beyond them: it is free (database only, no provider, no credits), the buckets are disjoint and complete, notRanking is derived rather than fetched, and the device parameter is a no-op on free sources. That is exactly the kind of extra context that adds value over structured fields.

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?

Front-loaded with the core purpose and mostly efficient, but goes slightly long with restated bucket invariants and a device caveat that is also covered in the schema. Still, every sentence carries useful information.

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?

Given no output schema, the description fully explains the return shape (the four buckets per run), their ordering (oldest first), the summation invariant, and the no-cost behavior. Nothing an agent needs to call it 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 parameters are already documented. The description reinforces the disjointness/summation invariant and calls out the device caveat, but adds no syntax or format details beyond the schema, so baseline 3 is appropriate.

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 verb+resource (per-run keyword-position-distribution buckets for a tracker) and explains precisely what is bucketed (top3/4-10/11-20/outside top20) per check run. Distinguishes itself from siblings like get_rank_keyword_history or get_rank_movers by emphasizing the distribution/trend answer.

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?

Gives a concrete use case ('is this domain's visibility trending up or down') and clarifies that no re-checking is needed. However, it does not explicitly name sibling alternatives (e.g., get_rank_keyword_history) or state when NOT to use it.

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