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

It discloses the financial side effect (charging the saved card), the need for user consent, and the fallback to a secure checkout link when no card or cardholder presence is required. This goes well beyond annotations' readOnlyHint=false and idempotentHint=false.

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 sentences: purpose, call pattern, and charge behavior/fallback. No filler, immediately actionable.

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 single-boolean-parameter tool, the description covers the full workflow, expected outputs (price, card, limit, or checkout link), and edge cases. No output schema exists, so this description carries that burden well.

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?

The schema already documents confirm's meaning (only true after explicit agreement). The description adds the orchestration detail of calling with false first to gather details, then true to execute, which enriches the parameter's usage 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 clearly states the action ('Buy more verification credits') and the context ('without leaving the conversation'). It distinguishes this from sibling tools by being the only purchasing tool among check_usage, estimate_claims, recall_claim, and verify_claims.

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 provides a concrete two-step calling pattern: first with confirm false/omitted to preview, then with confirm true after user agreement. This is explicit usage guidance, though it doesn't mention exclusions or alternative tools for other scenarios.

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