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

Annotations already cover read-only and non-destructive behavior, so the description adds value by disclosing the $0.005 USDC cost and x402 payment mechanism—information not present in structured fields. It also names the network (Base), which the annotations do not specify.

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?

A single sentence that front-loads the core action ('Check an ERC-20 token allowance on Base') and appends the cost detail. Zero filler words; every phrase earns its place.

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 fully described parameters and no output schema, the description covers the essential network and transaction cost. It could theoretically mention the return format, but that is not required given the tool's simplicity and the annotations' safety coverage.

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% and all three parameters already have clear descriptions. The tool description adds no additional parameter-specific meaning beyond restating 'owner' and 'spender', 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?

The description uses a specific verb ('Check') and resource ('ERC-20 token allowance') with the network ('on Base'), clearly distinguishing it from sibling tools like base_erc20_balance (balance vs allowance). No ambiguity about what the tool does.

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 intended use case is implied by the purpose (checking an allowance), but there is no explicit guidance on when to prefer it over, say, base_erc20_balance or base_eth_call. No exclusions or conditional routing are provided.

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