evm_get_balance

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

The description adds a behavioral limitation beyond the readOnlyHint: it explicitly excludes ERC-20 token balances, which is not implied by the annotation. It also confirms ENS name resolution for the address field, adding context. There is no contradiction with the readOnly/openWorld 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 two sentences, with the primary purpose front-loaded and the key exclusion in the second sentence. Both sentences contribute essential information, and there is no redundant or filler content.

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?

The tool is low-complexity with annotations and full schema coverage, and the description covers purpose, input scope, and exclusions. The only notable gap is the lack of return format (e.g., wei vs. ether) in the absence of an output schema, which prevents a perfect score.

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?

The input schema provides complete descriptions for both parameters (address as 'Wallet address or ENS name', chainId as 'Chain ID (defaults to runtime config)'). The description merely reiterates the address/ENS part and adds nothing about chainId or value formats, so the baseline 3 applies given 100% schema coverage.

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 uses a precise verb and resource: 'Get NATIVE token balance' for an address or ENS name, and it explicitly distinguishes itself from ERC-20 balance queries by naming evm_get_token_balance. This satisfies both the specific-resource and sibling-differentiation criteria.

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 provides explicit when-not guidance: 'This does NOT return ERC-20 token balances — use evm_get_token_balance for that.' It also clarifies the intended input ('address or ENS name'), making it clear when this tool is appropriate versus its ERC-20 counterpart.

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