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

Annotations cover safety (readOnlyHint) and open-world access, and the description adds non-obvious operational detail beyond them: no input needed, no charge when Base is unreachable, and x402 payment with a pointer to list_prices. These billing and failure-mode disclosures are genuinely useful and not derivable from annotations.

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 is returned, then when to use it, then input needs, then billing/failure notes. Every sentence carries distinct information with no repetition of the title or annotations.

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 input schema properties and no output schema, the description compensates by enumerating the returned fields and the three cost estimates. An agent knows enough to call it and interpret the result without further documentation.

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 explicitly says 'No input needed,' which correctly sets the expectation that this is a parameterless call.

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 scope ('Current Base mainnet gas') and enumerates exactly what it returns: gas price, base fee, priority fee in gwei plus estimated execution costs. This clearly separates it from sibling chain_* tools (balance, block, contract, token, tx) which return different data.

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 a clear use context: 'timing transactions and budgeting fees before sending.' It also routes the agent to list_prices for payment info. It stops short of explicit when-not-to-use or naming a concrete alternative for historical gas data, so not a 5.

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