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

Annotations already declare readOnlyHint and openWorldHint, and the description adds real value on top: it is a live on-chain read (not cached) and costs $0.005 USDC per call via x402, with the payment endpoint URL. It stops short of describing failure behavior or response shape, but the cost/freshness disclosure is exactly the kind of context annotations cannot carry.

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?

Two compact sentences, with the core capability front-loaded ahead of the pricing note. Nothing is redundant with the title or 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?

A read-only tool with no output schema needs the description to hint at return shape, and it doesn't — an agent cannot tell whether it gets two numbers, formatted strings, or token metadata. Pricing and freshness are complete, but the response contract is left open.

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 both parameters are already documented, which sets a baseline of 3. The description goes further by explaining the x402 payment model and per-call price, giving the agent the context needed to decide whether to supply the payment header or take the free-trial path.

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: reads live ETH and USDC balances for any address, scoped to Base mainnet. The chain qualifier implicitly separates it from the Solana siblings (solana_sol_balance, solana_usdc_balance), though no sibling is named outright.

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?

Nothing says when to pick this over wallet_portfolio (multi-chain) or the Solana balance tools; the agent must infer routing from the words 'Base mainnet'. No exclusions, prerequisites, or fallback guidance are given.

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