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

Annotations cover only readOnly/openWorld safety. The description adds substantial behavioral context the annotations do not: default 1,000 vs max 5,000 blocks, a 100-result cap, newest-first ordering, public-node refusal on large results, and a full cost model ($0.003 USDC per successful call via x402 on Base/Solana/Arc, failed calls not billed). This is exactly the non-structured behavior an agent needs.

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 result shape, then parameter detail, then constraints, then pricing — a logical order with little waste. It is slightly dense but every clause (defaults, cap, node limits, cost) carries information, so it is close to optimally sized.

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?

For a 4-param tool with an output schema, the description need not explain returns, yet it still summarizes result fields. It covers purpose, defaults, limits, failure modes, and pricing, leaving an agent nothing essential missing before calling.

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?

With 100% schema coverage the baseline is 3, but the description adds meaning beyond the schema: it supplies the default block window (1,000) that the schema omits (schema only states max 5000), gives a concrete topic0 signature example and the 32-byte-hash alternative, and states the 100-result cap. This meaningfully enriches parameter interpretation.

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+resource: returns event logs of a contract over recent blocks, with result ordering (newest first) and shape (block, tx hash, topics, data). An agent can tell this apart from evm_tx or evm_transfers by the log-oriented framing. It does not, however, explicitly name which sibling to prefer for related queries, so it falls short of a 5.

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?

Offers operational guidance ('narrow the range or add topic0' when nodes refuse large results), which is useful tuning advice, but gives no explicit when-to-use vs alternatives (e.g., evm_transfers for token movements, evm_decode for decoding). Usage is implied rather than routed.

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