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

With no annotations provided, the description carries the full burden of behavioral disclosure. It discloses that the API is paid, that it uses eth_call, and that it returns allowance information. However, it does not describe output format, error behavior, or whether the query parameters are all required, which are meaningful gaps for a paid external API call.

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 dense but each part earns its place: cost, functional semantics, upstream URL, HTTP method, and a concrete example. It is front-loaded with the paid nature and purpose. The example JSON is long but necessary because the schema lacks named query parameters, so it is justified.

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?

The description covers the key invocation details: paid cost, upstream endpoint, method, example parameters, and the meaning of the return value. However, there is no output schema and no mention of return format, units, or required parameter enforcement, so an agent may still be uncertain about the exact response shape and required fields.

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?

The input schema only describes generic 'body' and 'query' objects with no named properties, so the schema alone is not very informative. The description compensates by providing an explicit example query with contract, network, owner, and spender, giving the agent concrete parameter meaning beyond the generic 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 clearly states the tool's function: checking ERC20 allowance via eth_call, specifically how much a spender is approved to move from an owner's wallet. It provides an example query with contract, network, owner, and spender, making the purpose concrete. It does not explicitly differentiate from sibling tools, but the operation and resource are unambiguous.

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 provides an upstream URL, HTTP method, and example query, but gives no guidance on when to use this tool versus alternatives such as erc20_balance or other chain tools. There is no explicit when-to-use or when-not-to-use context, leaving the agent to infer usage solely from the stated purpose.

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