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

Annotations already mark this as read-only and non-destructive, so the bar is lower. The description adds valuable behavioral context beyond the annotations: the exact cost per call, the payment mechanism (x402 on Base), and the fallback behavior for unpaid calls.

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 short sentences, with the critical paid-per-call warning front-loaded. Every sentence earns its place and there is no filler.

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-parameter, read-only snapshot tool, the description covers output content and payment behavior sufficiently, and no output schema exists to complicate expectations. It is slightly vague about what the 'simple signal' actually is, but this does not block correct invocation.

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% and the lone asset parameter is fully documented with an enum. The description adds no real semantic detail beyond what the schema already provides, so the baseline 3 is appropriate.

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 returns current price, 24h/7d change, and a simple signal for a major crypto asset, so the core purpose is unmistakable. It does not explicitly differentiate this from the sibling pricecheck, but the resource and outputs are specific enough for an agent to understand what the tool does.

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 communicates that calls are paid and that unpaid calls return x402 payment terms, but it gives no guidance on when to choose this tool over siblings like pricecheck or crypto_regime. No exclusions, conditions, or alternative selection criteria are provided.

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