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

The description adds value beyond annotations by disclosing the return format: 'Returns balance in wei (hex and decimal) and in ether.' This is a behavioral detail not present in the readOnlyHint or openWorldHint annotations. It also clarifies that the balance is for the native token, avoiding ambiguity. No contradictions with annotations.

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 a single, well-structured sentence that leads with the action and resource, then specifies the return format. Every word earns its place—no wasted information or 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?

For a simple read-only balance query with a single parameter, no output schema, and annotations indicating read-only and open-world behavior, the description is fully adequate. It states the network, asset type, input nature, and output units, making the tool's behavior complete for an agent to select and invoke it.

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?

With zero schema description coverage, the description compensates by identifying the address as being 'on Ethereum mainnet' for native token balance. It adds network context beyond the schema's generic '^0x.*' pattern. The single parameter is straightforward, and the description sufficiently implies its purpose, though it doesn't elaborate on address formatting beyond the schema.

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 clearly states the action: 'Get native token balance for an address on Ethereum mainnet.' It specifies the resource (native token), the network (Ethereum mainnet), and the target (address). This distinguishes it from sibling tools like btc_get_balance and mezo_get_balance, and from eth_get_token_balance by explicitly saying 'native token.'

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 implies usage context: use this for native ETH balance on Ethereum mainnet. It differentiates from token balances via 'native token' and from other networks via 'Ethereum mainnet.' However, it does not explicitly mention alternatives or when not to use it, such as for testnets or ERC-20 tokens, so it falls short of full guideline coverage.

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