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

Annotations already declare readOnlyHint=false, openWorldHint=true, idempotentHint=false, destructiveHint=false, and the description adds materially beyond that: the $0.002 USDC x402 per-call cost (a rate/pricing constraint) and the interpretation of an unlimited approval as a risk signal. The non-read-only hint for a query tool is somewhat surprising, but it is consistent with the disclosed per-call payment rather than contradicted by the text, so no clear contradiction exists.

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?

Two sentences, zero filler: purpose/return contents first, then usage scenarios, then cost. The most decision-relevant information is front-loaded, and the pricing detail is short and factual.

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?

There is no output schema, yet the description enumerates the return payload (raw and formatted allowance, token symbol, decimals, unlimited flag), plus the cost model and the decision context for calling it. An agent has everything needed to invoke it correctly without external assumptions.

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 coverage is 100% and each parameter already carries a role description ("Wallet address that holds the token", "Address allowed to spend, usually a router or protocol contract", "ERC-20 token contract address on Base"). The description restates the owner/token/spender relationship as part of the purpose but adds no format, default, or constraint detail beyond the schema, so the baseline 3 applies.

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 precise verb and resource: checking a spender's ERC-20 allowance on Base, with the exact owner/token/spender triple implied. It also enumerates what is returned (raw and formatted allowance, symbol, decimals, unlimited flag), which cleanly separates it from base_token_balance and base_token_info in the sibling list.

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?

"Use before a swap or deposit to see if an approve transaction is needed, and to audit a wallet for risky unlimited approvals" gives two concrete triggering scenarios. It does not name an alternative tool or a when-not-to-use case, so it stops just short of the explicit routing guidance that would earn a 5.

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