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

With no annotations, the description carries the full load and does well: it discloses supported chains, the default chain (base), the priced cost ($0.002 USDC), and what the response contains. It doesn't state failure behavior for unsupported chains or malformed addresses, nor any rate limits, which keeps it from 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?

Two dense sentences, front-loaded with the usage trigger, then return shape, then chain scope, then price. No sentence is wasted, and the colon-delimited structure makes it scannable.

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 read-only allowance check with no output schema and zero schema coverage, the description covers return values, chain scope, default, and cost. Only the token identifier format and error cases are left implicit.

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 0%, so the description must compensate. It adds the default chain and clarifies the owner->spender direction, but leaves the format of 'token' (contract address vs symbol) and the address format for owner/spender unstated.

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 states a specific resource and relationship: 'ERC20 allowance owner->spender', plus the return fields (unlimited flag, owner balance, spendable-now). This lets an agent distinguish it from wallet_balances or token_check without opening the schema, though no sibling is named explicitly.

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?

It gives explicit trigger conditions: 'Use this before transferFrom/Permit/x402 flows or for approval hygiene'. That's clear when-to-use context, but there are no stated exclusions or named alternatives among the sibling tools.

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