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

Adds behavior annotations don't cover: it spends 2 lookup credits and requires user confirmation before running. That is exactly the kind of cost/auth-adjacent detail the agent needs. It stops short of saying whether results are cached or what happens if the user declines.

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?

Four short, front-loaded sentences with no filler. The opening is a noun phrase rather than a verb phrase, which is slightly less scannable than a 'Returns X for Y' construction.

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?

Cost and batch-limit context is solid and an output schema exists so return values needn't be explained. The missing piece is differentiation from the keyword-lookup siblings, which is the main ambiguity an agent must resolve to select this tool.

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 50%: countryCode is documented in the schema, keywords is not. The description's 'at most 20 keywords per call' merely restates the schema's maxItems: 20 and adds nothing about the string constraints (2–80 chars) or country defaults.

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 the resource (keywords the user names) and the exact outputs (volume, difficulty, intent), so an agent knows what it gets back. However, it never differentiates itself from siblings like lookup_keywords or research_keywords, which appear to operate on the same resource.

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 concrete operating guidance — confirm the 2-credit cost with the user first, cap at 20 keywords — but says nothing about when to choose this over lookup_keywords or research_keywords. Usage context is implied by the cost-confirmation rule rather than by explicit routing.

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