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

Annotations already declare readOnly, non-destructive, open-world, non-idempotent, so safety is covered. The description still adds real behavioral context: unknown hash returns 404 uncharged, failed calls are free, each successful call costs $0.01 via x402 USDC or card key, and the first 25 are free. It does not describe the response envelope or field types, which is the main remaining gap. A 3 reflects solid but incomplete disclosure beyond 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?

Front-loaded with purpose and alternatives, then input format, then pricing. Dense but every clause carries information. The pricing and example sentences make it longer than average, though they earn their place for a paid endpoint; minor run-on quality keeps it from a 5.

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?

There is no output schema, so the description compensates by listing exactly which fields come back. Combined with the input format, error behavior, and cost model, an agent has everything needed to call it and interpret the result without further context.

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% and the single parameter is already documented as a 0x-prefixed 64-hex hash, so the baseline is 3. The description reinforces the format and supplies a concrete example hash plus the 404-on-unknown consequence, which helps validation, but adds no new syntactic or semantic dimensions beyond the schema.

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 ("Look up an Arbitrum One transaction by hash") and enumerates the returned fields: sender, recipient, value in ETH, nonce, gas limit, 4-byte selector, block. It explicitly names the sibling tools arb_receipt and arb_logs as the places to go for complementary data, so the agent can discriminate without opening schemas.

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?

Gives a positive use case ("see what was sent or whether it exists") plus explicit routing rules: use arb_receipt for success/failure and fees, arb_logs for emitted events. No alternative is left implicit among the many *_tx/*_receipt/*_logs siblings.

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