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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the description doesn't need to repeat safety. It adds useful behavioral context beyond annotations: the decoding behavior (static types decoded, dynamic types shown raw and labelled), the reliance on Sourcify verification, the explicit output JSON structure, and the API key requirement. No contradictions with 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 compact yet information-dense, front-loading the core action and output, then covering usage, exclusions, output format, and constraints in a logical order. Every sentence earns its place—no fluff, no repetition.

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?

Given the tool's complexity and the absence of an output schema, the description adequately conveys the return shape (chain, address, function, selector, args, source) and key limitations (static vs. dynamic types, Sourcify dependency, API key requirement). It could mention error cases or what happens if the ABI isn't verified, but for most agent scenarios this is sufficient.

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%: chain, address, and data are fully described in the input schema with types and examples. The description does not add any additional parameter-level semantics beyond what the schema already provides, so it meets the baseline 3 but doesn't exceed it.

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 verb ('Decode'), the resource ('a transaction's calldata against the target contract's verified ABI'), and lists the specific outputs (function signature, selector, argument values). It also differentiates from siblings by naming get_abi, get_tx_status, and convert_evm, so an agent can immediately identify this tool's unique purpose.

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 explicitly states when to use the tool ('to explain what a pending or past transaction does') and when not to use it, naming exact alternatives for each exclusion ('Not for the whole ABI (use get_abi), a transaction's status (use get_tx_status), or computing a selector from a signature (use convert_evm)'). This provides unambiguous routing guidance.

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