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

With no annotations, the description must disclose behavioral traits itself. It does reveal that the route is free and that the data is 'current', which is useful context, but it omits details like authentication needs, rate limits, and output units. Still, the key free-preview trait is disclosed.

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 a single front-loaded sentence with no redundancy. It puts the core purpose first, then the free-preview note, then the chain list, making it highly scannable.

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 gives enough to select the chain and understand the high-level return values. It could clarify units of the gas price or transfer cost, but the tool is simple enough that an agent can call it 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?

The schema already fully documents the only parameter 'chain' with an enum and a default. The description's list of supported chains merely repeats the enum, adding no new meaning beyond what the schema provides.

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 states a specific resource ('Current gas price and estimated simple-transfer cost') and the supported chains, making the tool's intent unmistakable. It is clearly differentiated from sibling tools like x402_audit_merchant or x402_check_endpoint, which target different concerns.

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 phrase 'Free preview route' implies a lightweight, no-cost use case, and the chain list gives some context. However, it never explicitly says when to use this tool versus alternatives like x402_market_stats, and it offers no exclusions or when-not-to-use guidance.

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