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

No annotations are provided, so the description carries the full burden. It discloses the payment requirement ($0.01 per call, trial, no account), the need for a PAYMENT-SIGNATURE header on 402 challenge, and the retry behavior. However, it does not explicitly state whether the tool is read-only or idempotent, though it is implied by 'scan'. Slightly more detail on safety could elevate to 5.

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 four sentences, front-loading the purpose, then payment, then cold-start advice, then an alternative. Every sentence adds value, though some might consider it slightly verbose for the amount of information. Overall efficient and well-structured.

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?

Given the tool's complexity (paid, paywall protocol), the description covers the key aspects: what it does, how to pay (including trial), how to handle 402, and the best use case. No output schema is present, but the description implies a ranked list. A minor gap is not specifying the output format (e.g., symbol names), but it is sufficient for an agent.

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% (only one parameter, `limit`, with description 'How many to return (default 5, max 47)'). The description does not add additional meaning beyond the schema—it mentions 'most-top first' but that is ordering, not parameter-specific. Baseline 3 is appropriate as the description adds little beyond schema.

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 tool scans the FX snapshot for currency pairs at a top (sell), ranked most-top first. It distinguishes from sibling tools by mentioning the free `pitch` tool tells how many tops exist, while `scan_tops` names them. The verb 'scan' and resource 'FX snapshot' are specific, and the outcome is unambiguous.

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?

The description provides explicit when-to-use guidance: 'BEST COLD START: you do not need to pick a symbol — this ranks the whole universe for you.' It also contrasts with the `pitch` tool for counts and implies alternative tools for specific symbols (`evaluate_symbol`) or bottoms (`scan_bottoms`). The payment model and trial are clearly explained.

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