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

Beyond the readOnly/idempotent/openWorld annotations, the description discloses the data source (public RPC), the fact that the receipt is also fetched, the token formatting behavior (decimals/symbols), and a per-call price with payment rail ($0.01 USDC via x402 on eip155:8453). Cost and source disclosure are exactly the kind of operational context annotations cannot convey.

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?

Two sentences, front-loaded with purpose before detail, and every clause carries substantive content (scope, source, output fields, price). The second sentence is a long comma-chained list, but it is scannable and does not pad with marketing language.

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 must describe return contents — it does so thoroughly, covering status, fee, method decoding, and transfer events with formatting details. The main omission is that chain selection and the supported-chains list live only in the schema, and failure modes (nonexistent hash, unsupported chain) go unmentioned.

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 description never mentions either parameter. The `chain` field has schema documentation, but `hash` — the only required parameter — has no description in either the schema or the prose, leaving the agent to infer its purpose from the pattern alone. At 50% schema coverage, the description does not compensate for the gap.

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?

States a specific verb and resource ('Explain an EVM transaction') and enumerates exactly what the explanation covers: status, fee, decoded method, ERC-20/721 transfers. This clearly separates it from siblings like evm_contract, evm_balance, or evm_gas, which fetch other data for the same chain family.

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?

Usage is implied by the required transaction hash and the listed outputs, so an agent can infer it's for post-hoc inspection of a known tx. However, no sibling is named as an alternative and there is no explicit when-not guidance (e.g., use evm_contract for contract metadata, evm_gas for fee estimation).

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