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

No annotations exist, so the description carries full behavioral burden and does so richly: cost (2 credits for a typical 50-keyword lookup), a 100-row cap that silently drops the tail, non-paging billing model, and the advice to reconcile returned rows against keywords sent. This is exactly the disclosure an agent needs to avoid surprising costs or lost data.

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 value proposition, then cost/batching, then the cap caveat, then paging. Dense and mostly waste-free, though it is on the long side and interleaves cost, cap, and paging guidance rather than grouping them tightly.

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 fully describes the return shape (volume, difficulty, CPC, intent category, 12-month history) and covers cost, caps, and paging. 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 description coverage is 100%, so country, keywords, and language are already documented (including the fallback behavior for country). The description adds no syntax or format detail beyond reiterating the 100-keyword ceiling, 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 ('Find out whether a keyword is worth writing about') and enumerates exactly what it returns (search volume, difficulty 0-100, CPC, search intent, 12-month history). It explicitly distinguishes itself from Keyword_Rankings for keywords the site already ranks for, so an agent can route correctly without opening schemas.

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?

Explicit when-to-use ('keywords the site does NOT already rank for') and names the alternative ('Keyword_Rankings has measured data and is free'). It also gives a strong operating rule ('always batch them rather than calling once per keyword, as the cost is mostly per call'), covering both selection and invocation.

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