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

With no annotations provided, the description must carry the behavioral disclosure burden. It does add some context by naming the external data source (4byte.directory) and mentioning a trial limit of 5 free calls per registered wallet. However, it remains silent on whether the call is read-only, whether authentication is required, what triggers paid usage, or what the response contains, leaving significant behavioral ambiguity.

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 compact, front-loaded with the purpose, and contains no redundant words. The trial-limit note is useful additional information presented efficiently.

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?

This tool has 5 parameters, no output schema, no annotations, and a very large sibling list. The description gives a one-line purpose and a trial note but fails to clarify input semantics, output format, or how this lookup differs from closely related ABI tools. Combined with the uninformative schema placeholders, the definition is far from complete for an agent to invoke correctly.

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?

Although schema description coverage is 100%, every parameter description is a generic 'X to process' placeholder with no real meaning. The tool description itself does not explain any parameter either, so agents have no way to know what 'q' (query? selector? signature?), 'chain', 'contract', or 'chainId' should contain. The schema is not doing the heavy lifting here, so the baseline of 3 is not earned.

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 action (lookup) and a specific resource (Contract ABI via 4byte.directory), which clearly communicates the tool's function. However, it does not explicitly distinguish itself from sibling tools like x402-abi-decode or x402-abi-encode, so it falls just short of a 5.

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 implies the tool is used when a contract ABI needs to be looked up, but it provides no explicit guidance on when to choose this over sibling tools such as x402-abi-decode or x402-abi-encode, nor any warning about required setup (e.g., registered wallet). Usage context is only implied, not stated.

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