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

Beyond the readOnly/openWorld/destructive annotations, the description discloses the RPC block-window limit (up to 12000 blocks, fewer on busy tokens), that the response reports the searched range, and the x402 payment requirement with supported chains. This is rich behavioral context an agent needs before calling.

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-loads return format and ordering before limitations, pricing, and sample. Dense but every sentence earns its place; the inline example JSON is slightly verbose but useful for first-call correctness.

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 enumerates return fields and notes the response reports the searched block range. Combined with payment details and scope limits, an agent has everything needed to call it 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 is 3; the description adds genuine meaning by clarifying the holder filter matches transfers 'from or to one wallet' and that results are capped at 50 and ordered newest-first, which the schema does not spell out.

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?

Names a specific verb+resource: 'Recent Transfer events of an ERC-20 token', and enumerates the returned fields (tx, time, from, to, amount). This distinguishes it from metadata tools like erc20_info and native-transfer tools like evm_tx without naming them explicitly.

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?

'Use for quick wallet or token activity checks' gives clear context, and the block-range caveat ('cheap but not a full history') signals when the tool is insufficient. It stops short of naming an alternative for full history, so it is not a 5.

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