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

Adds substantial context beyond annotations: the return shape ('up to 100 logs'), the pricing/credits model, that failed calls are free, and an explicit reconciliation of why readOnlyHint=false ('not marked read-only because each call is charged'). Pricing and the read-only caveat are exactly the behavioral facts 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?

Front-loaded with the core action and scope, then alternative routing, then pricing. It is a single dense paragraph and the pricing/credits sentence is somewhat long, but each clause carries actionable information for an x402 agent.

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 still covers return contents (block, tx hash, topics), block-scan limits, filtering, cost, and the read-only flag rationale. Nothing an agent needs to invoke it 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 description coverage is 100%, so the schema already documents blocks, topic0 and address. The description restates the blocks range and clarifies topic0 as a '0x 32-byte event signature hash', adding only marginal detail over the schema. Baseline 3 is appropriate.

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 (List), resource (recent event logs), scope (contract on Arbitrum One, last N blocks) and optional filter. It also names the sibling arb_receipt for a different use case, so an agent can separate this from the other arb_* tools immediately.

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?

Explicitly says what it is for ('watch transfers or contract events') and names the alternative and the condition that selects it ('for one transaction's outcome use arb_receipt'). When-to-use and when-to-use-something-else are both present.

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