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

Beyond the annotations it discloses failure semantics (a reverting transaction returns 422 with the reason, uncharged), the billing model ($0.01/call via x402 USDC or card key, first 25 free, failed calls free), and that repeats are charged. That last point also explains why idempotentHint=false holds for an otherwise read-only tool, which is a genuinely useful reconciliation.

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?

Front-loaded with purpose and return units, then arguments, then the sibling alternative, then failure and billing behavior. Nearly every sentence carries information, though the example address and the pricing boilerplate add length that a caller only needs once.

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?

There is no output schema, so the description carries the full burden of describing the return value — and it does, naming all three units. Combined with failure semantics and cost model, an agent has everything needed to call this correctly and interpret results.

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%, so the schema already documents all four parameters and the 3 baseline is met. The description adds real nuance by noting value is denominated in POL and that 'from' matters only 'when the call depends on it' — meaning sender-dependent estimation — which the schema's '(default: an empty address)' does not convey.

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 and resource (estimate gas for a transaction on Polygon PoS), names the underlying RPC method, and specifies the three units returned (gas units, gwei, POL). It explicitly distinguishes itself from polygon_gas, the gas-price-only sibling, so an agent can route correctly without opening a 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 both when to use ('before sending a transaction or to price a batch') and when not to ('for the gas price alone use polygon_gas'), plus the argument requirements for a contract call vs a plain transfer. This is explicit routing guidance, not implied usage.

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