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

Annotations declare readOnlyHint=false, openWorldHint=true, and idempotentHint=false, and the description explains why the write-ish profile exists: cache misses trigger a billable lookup, and results come from a 30-day cache. It also pins the batch limit (50 terms, one country/one language). It stops short of stating auth requirements or rate limits, so it is strong but not exhaustive.

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?

Three tightly packed sentences: trigger first, payload second, billing/cache caveat third, exclusion last. No sentence is redundant with the title or the schema.

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?

An output schema exists, so return-shape detail is unnecessary. For a billable, cached, multi-term lookup the description covers the trigger, scope limits, cost implication, and source caveat (Google web search vs app-store counts) — 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%, and the schema already documents terms, country, and lang with patterns and limits. The description reinforces the one-country and up-to-50-words constraints but adds no syntax or format meaning beyond the schema, so the baseline 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 verb+resource (keyword search volume) and immediately frames what is returned: monthly Google web-search volume, difficulty, CPC, competition. It distinguishes itself from get_keyword_rank and get_keyword_history by explicitly disclaiming rankings.

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?

Opens with an explicit when-to-use trigger ('when someone asks how popular a keyword is or which keyword ideas are worth targeting') and closes with an explicit when-not ('Not for rankings'), which routes the agent to the sibling rank tool.

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