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

The readOnlyHint annotation already discloses that this is a safe read operation. The description adds useful context by mentioning the portfolio overlap, but does not go deeper into behaviors like return format, error handling, or network specifics beyond schema. With annotations carrying the safety profile, this is adequate but not rich (consistent with the calibration example).

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?

The description is exactly two sentences. The first sentence states purpose, the second provides a critical usage note. No redundant words, no filler. Every sentence earns its place, and the note about get_wallet_portfolio is essential for correct tool selection.

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?

For a simple 2-parameter read-only tool with an output schema, the description covers what it does, when to use it, and which sibling to avoid. The existence of an output schema means return-value details are not required in the description. It is complete within the context of the tool's complexity.

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%: both address and chain_id are fully described in the input schema. The description adds nothing new about the parameters themselves, only reinforcing the Ethereum/Base chain support. Baseline of 3 applies because the schema does the heavy lifting.

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 ('Get'), a clear resource ('native ETH balance'), and a scope ('Ethereum or Base address'). It explicitly distinguishes itself from get_wallet_portfolio, which is a sibling tool, by noting the balance is already included there. This is a precise, non-tautological purpose statement.

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 explicit guidance on when to use the tool ('only call get_eth_balance when you need a standalone ETH balance without a full portfolio scan') and names the alternative (get_wallet_portfolio). This is a clear usage vs. alternative distinction, exceeding mere implied context.

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