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

The description says 'Read a live ERC-20 allowance', which strongly implies a read-only operation, but the annotations declare readOnlyHint=false. This is a direct contradiction in the tool's safety profile. The description does add useful context like price, payment method, and return format, but the contradiction forces a score of 1.

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 three tight sentences with no filler. It front-loads the action and resource, then gives return details, price, and the key x402 parameter guidance. Every sentence carries operational value.

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 tool with no output schema, the description adequately states what is returned ('current block and raw token units'). It also communicates the paid nature and the optional salt ID. It does not fully explain the x402 challenge flow, but the input schema's description of _x402_payment_signature covers the required behavior, so the definition is reasonably complete.

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 50%, and the three required address parameters have no schema descriptions. The description partially compensates by explaining their role in the allowance query, and it adds guidance that _salt19_operation_id is recommended but optional. The x402-related optional parameters are already described in 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 names a specific action ('Read'), a specific resource ('ERC-20 allowance on Base'), and the exact scope ('an owner/spender pair'). It also states the return value ('current block and raw token units') and a differentiator ('without an API key'), making it easy to distinguish from sibling tools like base-token-balance or base-contract-state.

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 clearly implies the use case: when you need an ERC-20 allowance on Base for a specific owner/spender pair. It does not explicitly name alternative tools or state when not to use it, but the context is specific enough that an agent can route correctly.

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