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

Annotations already establish readOnlyHint, idempotentHint and destructiveHint=false. The description adds genuinely non-annotated context: no wallet, no payment required, and zero arguments. Return format is not described, but as a shape-preview tool that gap is minor.

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?

A single front-loaded sentence. The cost/benefit framing ('[FREE]' ... 'before paying') leads, and every clause earns its place.

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 no-argument preview tool with no output schema, the description supplies what an agent needs: cost, prerequisites (none), and intent. It does not hint at what fields the sample response contains, but that is what the call itself reveals.

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?

Zero parameters, so the baseline is 4. The description reinforces this by explicitly stating 'no arguments needed', which matches the empty 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?

States a specific verb+resource: it returns a sample response for gas_price. The '[FREE]' marker and 'before paying' clause distinguish it cleanly from the paid gas_price sibling without needing to open either schema.

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?

Gives clear context for use: run this to see the response shape before spending 0.002 USDC. It stops short of explicitly naming gas_price as the follow-up alternative, but the implied workflow is unambiguous.

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