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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), yet the description adds genuinely new operational facts: a price of 0.004 USDC per call, p95 latency of 1200 ms, and that balances are read in a single block (an atomic snapshot). It stops short of describing failure modes or rate limits, so it is strong but not exhaustive.

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 the return shape, then usage, then exclusions, then cost and latency. The 'Use when you need the ERC20 token balance or wallet balance...' clause partially restates the opening sentence, which is the only real redundancy.

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?

An output schema exists, so return values need not be detailed, and the description still summarizes the payload. Combined with cost, latency, chain scope, default token set, and explicit exclusions, an agent has everything needed to invoke it correctly.

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 adds meaning beyond the schema by disclosing that 21 major tokens are queried by default, which explains the semantics of the optional 'tokens' array as an additive list rather than a filter.

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: returns ETH and ERC20 token balances for a wallet on Base, read on-chain in one block. It is clearly distinguishable from siblings like token-price_v1 (prices, not balances) and explicitly scopes itself to Base.

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 an explicit when-to-use condition ('need the ERC20 token balance or wallet balance of an address on Base for onchain data checks') and an explicit when-not list (Ethereum mainnet or other chains, NFTs, transaction history, USD values). This is exactly the routing information an agent needs against the sibling set.

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