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

Annotations are present (openWorldHint=true, readOnlyHint=false, etc.), so the bar is lower, and the description still adds material context they don't carry: the $0.001 USDC-on-Base cost per successful call via x402 payment. That payment obligation meaningfully explains the readOnlyHint=false designation and warns the agent before calling. It does not disclose freshness/caching or rate-limit behavior, so not a 5.

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, front-loaded with what it returns, then when to use it, then cost. Every sentence earns its place and nothing is redundant with the empty schema.

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 no parameters and no output schema, the description carries the full burden and does so: it enumerates the returned values and the POL-transfer estimate, states usage timing, and discloses the per-call cost. Nothing an agent needs to invoke it correctly is missing.

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 tool takes zero parameters, so there is nothing for the description to clarify beyond the schema. Baseline 4 applies for a no-parameter tool.

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 resource and chain ('Current gas on Polygon PoS') plus exactly what is returned: gas price, base fee, suggested priority fee in gwei, and the cost of a 21,000-gas POL transfer. This cleanly separates it from sibling chain tools like arb_gas, base_gas, eth_gas, and op_gas without needing the 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?

Explicitly names the trigger conditions: 'Use before sending a transaction or to decide whether to wait.' That is clear contextual guidance. It stops short of naming an alternative tool or any exclusion, so it lands at 4 rather than 5.

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