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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds genuinely new behavioral context the annotations cannot express: this is a paid x402 route costing $0.90, which tells the agent a payment flow is involved. It stops short of explaining the two-call challenge/retry pattern, though the payment parameter's schema text carries that burden.

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 short clauses that front-load the capability and then the endpoint/price. Nothing is wasted, though the telegraphic style (em dash plus price fragment) borders on under-specification rather than crispness.

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 3 simple params, full schema coverage, and read-only annotations, the essentials are present. The gap is the return shape: no output schema exists, and "scores and language" only gestures at the response format (score scale? language as ISO code or name?) without pinning it down.

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 text, payment, and maxKeywords are all documented at the field level with the 24k char limit and the full 402 proof mechanics. The description adds nothing about parameters, so the baseline 3 applies; it neither compensates nor detracts.

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 and resource ("AI keyword extraction") plus the outputs it produces ("scores and language"), which is more than a restatement of the name. However, it never distinguishes itself from the similarly-shaped sibling classify_text or from run_seo_audit, so an agent must infer the boundary itself.

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?

There is no statement of when to reach for this tool versus classify_text, run_seo_audit, or get_page_roast, and no exclusions or prerequisites beyond the price tag. The agent gets the endpoint and cost but no selection guidance.

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