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

Annotations already declare readOnly/openWorld/non-destructive/non-idempotent, so the bar is lower, but the description still adds real context: 8 KB calldata cap, reverts return 422 with the reason and are uncharged, execution pinned to the latest block, and the pricing model ($0.01/call, first 25 free). The 'repeats are not free' note is consistent with idempotentHint=false rather than contradicting it.

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 what the tool is and when to use it, and every sentence contributes (limits, pricing, revert behavior). It is a single dense paragraph and the pricing/credits detail is slightly over-weighted relative to its selection value, keeping it just under 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?

No output schema exists, and the description discharges that burden by explaining the return is raw undecoded return data that must be decoded with the function's ABI. Together with block semantics, revert behavior, and cost, an agent has everything needed to invoke and interpret the result correctly.

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 baseline would be 3, but the description adds meaning beyond the schema: the calldata format is spelled out (4-byte selector plus arguments) and demonstrated with a real selector, and the 8 KB size limit is only stated here. The optional 'from' parameter is left to the schema, which is acceptable given full coverage.

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 ('Read-only contract call on Arbitrum One (eth_call)') plus the exact scope: ABI-encoded calldata to a contract at the latest block, raw return data, no transaction or gas. It also distinguishes itself from the family of dedicated readers like arb_token_balance/arb_token_info by saying it covers 'any view function that has no dedicated tool'.

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 routes the agent: use this for view functions lacking a dedicated tool, and the concrete example (USDC totalSupply, selector 0x18160ddd) shows the intended call shape. Cost and retry conditions (charged per call, repeats not free, failed calls free) are stated, which is the practical guidance an agent needs before calling.

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