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

Annotations already establish read-only, idempotent, non-destructive, open-world behavior, and the description adds substantial context beyond that: external lookup in 4byte.directory, built-in signature table, Keccak-256 re-hashing, candidate ranking, ABI decoding details, and pricing. There is no contradiction with the annotations.

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 front-loaded and dense with useful information, but it is essentially one long multi-clause sentence with a lengthy type enumeration. It earns most of its space, yet could be structured more cleanly.

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 no-output-schema, fully optional-parameter tool, the description gives strong behavioral context and explains candidate ranking and decoding. It omits the expected response shape and does not state that at least one of selector, topic, calldata, or signature must be supplied, which is a meaningful gap.

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%, so the baseline is 3. The description adds meaningful semantics by explaining that calldata is ABI-decoded against candidates, signatures are hashed into selectors/topics, and candidates are ranked by clean decoding, though it does not clarify the required combination of optional parameters.

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 verb and resource: decoding EVM function selectors, calldata, and event topics, plus computing selectors/topics from signatures. It clearly distinguishes this selector-decoding utility from general EVM read/info tools 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?

It gives a clear context for use by naming the input modes (selector lookup, topic lookup, calldata decoding, signature hashing). However, it does not explicitly state when to prefer this over adjacent tools such as evm_read or evm_contract_info, nor does it state exclusions.

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