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

With no annotations at all, the description carries the full behavioral burden. It does usefully disclose the $0.05 charge and that the response includes normalization and checksum status, but it never clarifies that this is an offline format/checksum test rather than an on-chain lookup — a meaningful ambiguity given the name 'onchain_address_check' and the chain_* siblings. It also omits whether invalid input still incurs the charge.

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?

Two tight sentences with the price front-loaded and the operation and return value following immediately. No filler or redundant restatement of the tool name.

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 one-parameter validator with no output schema, the description covers purpose, cost, and the shape of the result, which is nearly everything an agent needs. The remaining gap is the ambiguity between 'onchain' in the name and the purely local format/checksum check described, plus what normalization entails.

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% for the single address parameter, and the schema already supplies the 0x-prefix requirement and a worked example. The description adds nothing about input handling (e.g. non-prefixed or lowercase input, mixed-case checksum failures), so baseline 3 applies.

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?

The description gives a specific verb and resource: validate an EVM address format and EIP-55 mixed-case checksum, plus a stated return of valid/invalid. That is clearly distinguishable from the chain_* siblings, which read chain state. It does not explicitly name a sibling or scope boundary, so it stops 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?

Usage is implied by the validation framing (check a 0x address before using it), but the description never says when to call this versus chain_ens_resolve or when validation is unnecessary. There are no exclusions or preconditions stated, so the agent must infer the call context.

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