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

While annotations already declare readOnlyHint=true and openWorldHint=true, the description adds a key behavioral trait: 'Pure computation — no RPC call needed.' This goes beyond the read-only annotation by clarifying that no network interaction occurs. No contradiction with annotations; it complements them.

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 three sentences with no fluff. It front-loads the main action, then adds the pure-computation note, then gives input guidance. Each sentence earns its place; it is appropriately sized for the tool's simplicity.

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 simple two-parameter decode tool with no output schema, the description provides sufficient information: what it does, the input source, the operational nature (pure computation), and a hint of the output contents. It works well with the annotations and schema to give an agent complete guidance.

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 schema covers both parameters (calldata and abi) with descriptive text, giving a baseline of 3. The description adds value for the calldata parameter by specifying its source ('from a transaction input or eth_call'), which is a meaningful hint beyond the schema's 'Raw calldata (0x-prefixed hex)'.

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 ('Decode') and resource ('raw calldata'), states the output ('function name and typed arguments'), and specifies the method ('using a provided ABI') and network ('on Mezo'). This clearly distinguishes it from sibling tools like eth_decode_calldata and the testnet variants.

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 clear context on when to use the tool ('Pass the hex calldata from a transaction input or eth_call') and notes that it is pure computation with no RPC call. It does not explicitly mention alternatives or exclusions, but the context is sufficient for an agent to determine when this tool is appropriate.

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