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

Annotations only declare the safety profile (readOnlyHint=false, idempotentHint=true), and the description adds substantial context beyond them: the $0.25 USDC cost, accepted chains (Base or Arbitrum One), the x402 v2 PAYMENT-SIGNATURE header requirement, the paid_url endpoint, and a docs link. It does not cover failure/refund behavior when payment succeeds but the request fails, which is the remaining gap; readOnlyHint=false is consistent with charging and minting a receipt.

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?

Despite packing purpose, defaults, the raw alternative, payment mechanics, cost, and endpoint into a few short segments, nothing is wasted and the core purpose is front-loaded. Each fragment carries operational information an agent needs before calling.

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 an output schema present, return-format explanation is correctly omitted, and the description covers what the schema and annotations cannot: payment protocol, cost, auth header, and endpoint. The main omission is the practical prerequisite of having a funded x402-capable payer and what happens on payment failure.

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% and the idempotency_key semantics (replay returns the original receipt, per-tool/per-payer scoping) are fully documented in the schema. The description's default notes ('type defaults ondemand; omit gpu = all classes') restate what the schema already says, so it adds little beyond the baseline 3.

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 uses a specific verb-and-resource framing ('GPU price, sealed proof: snapshot, cheapest ask/class, signed receipt') and names the sibling compute_spot_prices as the 'Raw' counterpart, so an agent can distinguish sealed-receipt pricing from raw pricing. It stops short of a single crisp sentence stating the operation, but the scope is clear.

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 gives implied guidance through 'Raw: compute_spot_prices' and default notes ('type defaults ondemand; omit gpu = all classes'), but never explicitly says when to choose the sealed variant over the raw one or what preconditions exist (wallet/payer setup, funding). The alternative is named without a condition that selects it.

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