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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, idempotentHint=false), and the description adds value beyond them: reverting transactions return 422 with the reason and are uncharged, each successful call is billed at $0.002 via x402 USDC or card key with the first 25 free, and retries are not free. That is exactly the operational context annotations cannot express.

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 what the tool does and when to use it, then examples, error semantics, and billing. The billing sentence is longer than strictly needed for tool selection but carries decision-relevant cost information, so only minor trimming would be warranted.

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 four-parameter read-only estimation tool with no output schema, the description covers return units, error behavior, cost, and the one non-obvious parameter interaction (from). 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?

Schema description coverage is 100%, so the baseline is 3. The description still adds meaning beyond the schema: it clarifies that value is denominated in ETH, that calldata is for a contract call, and notably that the sender matters only when the call depends on it, which guides correct use of the optional from field.

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 concrete verb and resource with the underlying RPC method (eth_estimateGas on Base) and the exact output dimensions (gas units, gwei, ETH). It is immediately distinguishable from base_gas and base_call by naming what it computes versus what those return.

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 explicit when-to-use (before sending a transaction, pricing a batch) and an explicit alternative with its selecting condition ('for the gas price alone use base_gas'). The revert case and the billing conditions are also stated, leaving nothing to inference.

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