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

With no annotations, the description carries the burden. It discloses the two-phase workflow (terms then payment), the cost, and that payment completes the purchase within the same tool call. However, it doesn't specify what the response looks like when terms are returned or what happens if payment fails, which is a minor gap given the paid nature.

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 compact and front-loads the core value (real costs) before procedural details. Every sentence earns its place; no fluff.

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 tool with one optional parameter and no output schema, the description covers the workflow and cost adequately. The only minor omission is what the returned data looks like (e.g., a table of percentiles), but the high-level outcome is clear. It's sufficient for an agent to proceed correctly.

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% for the single `payment` parameter, so the schema already describes it as a signed x402 payment. The description adds context on how to use it (the two-call workflow) but not much beyond. Baseline 3 is appropriate given high schema coverage.

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 reports actual Arc transaction costs with percentiles and sample sizes, distinguishing it from quoting docs. It also mentions the specific cost ($0.004 per call) and the payment workflow, making its purpose unmistakable.

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 explicit instructions: call once without `payment` to get the terms, sign them, then call again with `payment`. It implies this is the tool for Arc gas costs, standing apart from siblings like arc_cctp_cost or arc_x402_stats, and tells the agent exactly when to use it.

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