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

Annotations cover only readOnly and openWorld, so the description adds substantial unseen context: public-RPC aggregation with no API key, pay-per-call in USDC/USDT on Base via x402, and a 3-call free tier per wallet. It stops short of stating rate limits, cache behavior, or failure modes on unpaid calls, which would be needed for 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 dense sentences, front-loaded with what is returned and followed by data source and payment mechanics; each sentence carries information. Slightly compressed by abbreviated phrasing ('3 free calls per wallet'), but there is no filler.

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 output schema, the description steps in to describe the return shape (tiered fees plus per-transaction USD costs) and the chains covered, and it explains the payment prerequisites an agent must satisfy. Cache/pagination and error semantics for unpaid calls remain unspecified, so it is strong but not exhaustive.

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% and the schema already documents every parameter, including the default chain 'base' and the wallet-unlocks-free-tier behavior that the description merely echoes. The description adds no format, range, or interaction detail beyond what the schema provides, so the baseline 3 applies.

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?

The description names the concrete resource (live EIP-1559 gas fees with slow/standard/fast tiers), the derived output (USD cost per transaction type across transfer, ERC-20 transfer, swap, NFT mint), and the exact chain set. An agent can tell this apart from token_price or market_spread without opening any 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?

Usage is only implied: an agent infers it should call this when it needs gas estimates or per-transaction cost data. There is no explicit statement of when to prefer this over token_price/market_spread, and no mention of when not to use it (e.g., for historical fees).

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