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

Annotations declare readOnlyHint and openWorldHint, so the safety profile is already covered. The description adds genuinely useful behavior beyond that: balances are read live from chain, only non-zero balances are returned, and no pricing or advice is produced. It does not cover pagination or failure modes, but for a read tool that is minor.

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 short sentences, each carrying distinct information, with the core capability front-loaded and the exclusions at the end. Nothing is redundant or padded.

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 carries the burden of explaining results and does so partially by stating only non-zero balances appear and no price data is included. What the balance entries actually look like (amounts, decimals, symbols) is left unstated, a small remaining gap for a 2-param read tool.

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 both parameters carry their own descriptions and patterns, so the schema does the heavy lifting. The description's mention of 'any address on Base' and 'extra token contracts you list' mirrors the schema and does not add syntax or format detail beyond it.

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+resource with scope: ETH plus a named list of major tokens for any address on Base, plus user-supplied extras. This clearly separates it from base_erc20_balance (single token) and solana_wallet_balances (different chain) without opening either 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?

The description establishes clear context (live multi-token balance read for one address, extensible with up to 20 extra contracts). It also bounds expectations by ruling out price data and recommendations, but it never explicitly names an alternative tool or states when to prefer this over base_erc20_balance.

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