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

With annotations covering safety (non-read-only, non-destructive, non-idempotent, closed-world), the description adds substantial behavioral context: auth requirements, eligibility rules for PAY_AS_YOU_GO, balance visibility, Stripe Checkout link behavior, credit expiration, and anonymous fallback. This is rich beyond what the annotations provide.

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?

The description is front-loaded and information-dense with no obvious filler, but it is a single long paragraph covering several conditional branches. It is appropriately sized for the complexity, though bullet-like structure would improve scanability.

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?

For a one-parameter, no-output-schema tool, the description covers all key call paths: listing options, purchasing available packs, subscriber-only top-ups, anonymous handling, and where larger options live. Nothing essential for correct invocation appears 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 the baseline is 3; the description goes further by explaining that PACK_5/15/30 are purchasable here, that PAY_AS_YOU_GO is limited to signed-in plan subscribers, and that larger packs are elsewhere. It does not add syntax or format details, but it meaningfully enriches pack eligibility semantics.

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?

The description names the specific resource (credit packs for Underpriced AI scans) and the core action (pay/buy), and details what each pack selection returns. It clearly differentiates this payment-related tool from the sibling scan/research tools, which have unrelated purposes.

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?

It states exactly when each path applies: no pack lists packs and balance, PACK_5/15/30 return a Stripe Checkout link, PAY_AS_YOU_GO is only for signed-in plan subscribers whose plan scans run out, and anonymous callers get the pricing page. Alternatives for larger packs and monthly plans are also routed explicitly.

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