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

With no annotations, the description carries the full behavioral burden. It does disclose an important operational fact — $0.005 per call paid over x402 (USDC) — which is valuable and not in any structured field. However, it does not say what happens on a malformed/invalid signature (error vs. false), so behavioral coverage is partial.

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?

Three short sentences, front-loaded with the core action, then the use case, then the cost. Every sentence earns its place; no filler or repetition of schema content.

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 or annotations exist, so the description must carry return semantics — and it does, stating both the recovered address and the match result. Cost/payment is covered; only failure-mode behavior is left unstated, which is a minor gap for a 3-parameter tool.

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 baseline is 3. The description adds genuine meaning beyond the schema by framing the flow: the message is a personal_sign/EIP-191 payload and the recovered signer is compared against the 'expected' address, clarifying the role of the optional parameter.

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 precise verb+resource: recovers the signer address from a personal_sign (EIP-191) message and reports whether it matches. No sibling tool performs signature recovery, so an agent can distinguish this from util_address, util_keccak256, or the evm_* tools unambiguously.

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?

"This is how you prove a wallet is controlled by whoever is talking to you" gives a clear use context (authentication / ownership proof). It stops short of naming when-not to use it or pointing at alternatives, so it is context without exclusions.

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