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

Annotations already declare readOnlyHint, openWorldHint, destructiveHint=false and idempotentHint=false; the description still adds real signal beyond them: unknown hash returns 404 uncharged, failed calls are free, each call is metered so repeats cost money (which is what idempotentHint=false actually implies for billing). It also restates the no-side-effects guarantee, reinforcing rather than contradicting the 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 routing before pricing and example detail, and every clause carries information. It is a dense single block though — pricing, example, and safety caveats are stacked together rather than separated, which costs a little scanability.

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?

One required parameter, no output schema, annotations present — and the description still covers return fields, the not-found case, cost model, and side-effect profile. Nothing an agent needs in order to decide and call correctly is missing.

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%, so the baseline is 3; the description earns extra by supplying a concrete worked example hash and the error semantics of an unknown value (404, uncharged). It doesn't add anything about the hash format beyond the schema, but the example and failure behavior are genuine value-adds.

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 ("Look up an Arbitrum One transaction by hash") followed by an enumeration of what comes back (sender, recipient, value in ETH, nonce, gas limit, selector, block). It explicitly carves itself away from arb_receipt (success/failure, fees) and arb_logs (events), so an agent can pick the right sibling 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 an explicit use case ("see what was sent or whether it exists") and names both alternatives with the condition that selects each. This is the when/when-not/alternatives pattern at full strength.

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