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

Annotations already establish readOnly/idempotent/non-destructive, and the description adds genuinely new operational context: $0.005 USDC per successful call via x402 on Solana, plus an equivalent HTTPS endpoint. It does not cover failure behavior (unknown hash, reorged/unsupported chain), which keeps it below 5.

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?

Front-loads the core action and payload list, then moves to the operational facts (read-only, price, HTTPS alternative). The returned-field enumeration is a long run-on list but every element is informative; no filler sentences.

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?

With no output schema, the description carries the burden of describing return values, and it does so thoroughly by enumerating the decoded fields. Missing pieces are error/edge-case behavior and pagination/response shape, which for a single-transaction lookup are minor.

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% — both 'hash' (0x-prefixed 32-byte) and 'chain' (enum with default 'eth') are fully documented in the schema. The description only restates the chain names in prose and adds no syntax, format, or default guidance beyond what the schema already provides, so baseline 3 applies.

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?

Specific verb + resource ('Decode an EVM transaction') with the supported chains (Ethereum, Base, Arbitrum) and a full enumeration of what is returned (status, gas, fee, selector, ERC-20 Transfer/Approval events). It does not explicitly distinguish itself from nearby siblings such as evm_selector_decode, evm_token_transfers, or evm_read, so it stops 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 establishes the operating context (read-only, public RPC, paid per call) but never states when to pick this over evm_token_transfers (for event logs only) or evm_read (for arbitrary contract reads). Usage is implied by the resource type rather than guided.

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