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

Annotations already declare readOnlyHint and idempotentHint, and the description adds meaningful behavioral context: it returns 'raw units and decimals provenance' and is 'preflighted so you never pay during an RPC outage'. This goes beyond the structured annotations without contradicting them.

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 sentences with no wasted words. The core scope is front-loaded, followed by key behavioral details and the preflight safety guarantee.

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 a full input schema, an output schema, and annotations covering read-only/idempotent behavior, the description supplies the remaining essential context: combined ETH + token coverage, default token, raw units/decimals, and RPC-outage protection. Nothing critical is missing for correct invocation.

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 schema already documents address and token_address well. The description reinforces that token_address defaults to USDC on Base but does not add substantial new meaning beyond what the schema provides.

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 states a specific verb and resource: 'On-chain balance snapshot: native ETH balance plus one ERC-20 token balance (defaults to USDC on Base)'. This clearly distinguishes it from sibling tools like erc20_balance, which likely covers only token balances, and crypto_ticker, which is not an on-chain snapshot.

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 gives clear context: use this when you need both native ETH and one ERC-20 token balance, with a default of USDC on Base. However, it does not explicitly state when to prefer this over alternatives like erc20_balance or when not to use it, leaving some inference to the agent.

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