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

With no annotations, the description carries the full burden and does well: it discloses the underlying mechanism (eth_call to the allowance method), the pricing model ($0.005 per call paid over x402 in USDC), and the two-part return (remaining amount plus an unlimited flag). It omits rate limits and any failure/error behavior, keeping it short of a 5.

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?

Three sentences, front-loaded with the core question the tool answers, then usage context, then mechanism and cost. Every sentence carries information, though the 'finds forgotten infinite approvals' phrasing is slightly promotional rather than strictly functional.

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?

No output schema exists, and the description compensates by explaining what is returned (remaining allowance and unlimited-approval status). Combined with the transport and payment details, an agent has enough to call it correctly; error handling and rate limits remain unstated.

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 owner, spender, token and chain are already documented in the schema. The description reinforces the owner/spender relationship conceptually but adds no syntax, format, or default guidance beyond what the schema provides — the baseline 3.

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?

States a specific verb+resource: reads the ERC20 allowance a spender has over an owner's tokens, and additionally reports whether the approval is unlimited. This clearly distinguishes it from sibling readers like evm_erc20_balance and evm_token_info.

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?

Gives concrete usage context — 'the check to run before an approve' and 'the one that finds forgotten infinite approvals' — which tells the agent when this tool is the right one. It does not explicitly name an alternative tool to use instead, but the intended scenarios are clear.

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