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

With no annotations, the description carries the full burden and does well: it discloses the tool is tolled ($0.02 USDC per call), the accepted payment chains and protocol (Base or Solana via x402), and crucially the failure behavior (returns 402 instructions instead of data). It stops short of rate limits, latency, or return shape.

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 tight sentences, zero waste, with the identity and the tolling/payment constraint front-loaded before the fallback behavior. Every sentence 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 zero-param read tool with no output schema, the description covers identity, cost, payment path, and the unpaid fallback, which is what an agent needs to invoke it correctly. Missing only minor details like return format breadth or per-chain coverage specifics.

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 confirms 'No params', which is consistent with the empty schema and leaves nothing ambiguous.

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?

It states a specific verb+resource ('live gas prices per chain') and adds an audience qualifier ('for agents about to move money'). It does not explicitly name a sibling like bridge_prices, but the resource is specific enough to distinguish it from the other bridge_* tools.

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 'for agents about to move money' implies the usage context, and the toll notice implies a payment prerequisite. However there is no explicit when-not guidance or named alternative (e.g. bridge_prices) for agents who want prices without paying.

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