verify_x402_signature

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

Annotations already establish readOnly, idempotent, non-destructive, closed-world behavior, but the description goes further by disclosing the verification algorithm (recover signer with eth_account), the case-insensitive address comparison, and the returned fields. No failure modes or malformed-signature handling are described, which keeps it short of a 5.

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, front-loaded with purpose and mechanism; the second sentence about return values is mildly redundant given the output schema but costs little.

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?

An output schema exists and annotations cover the safety profile, so the description only needs to convey mechanism and comparison semantics, which it does fully. Nothing essential for correct invocation is missing.

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 all three parameters are documented in the schema; the description only reinforces mandate_json as the signed payload and adds the case-insensitive comparison detail. With the schema doing the heavy lifting, the baseline of 3 is appropriate.

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 (verify) and resource (x402 EIP-191 personal_sign over the mandate JSON), and names the recovery mechanism (eth_account) so an agent can distinguish it from the EIP-712 sibling validate_eip712_permit without opening either schema.

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 signature scheme named in the description (EIP-191 personal_sign over mandate JSON), which implicitly routes the agent away from validate_eip712_permit. However, no explicit when-to-use/when-not statement or named alternative is given, so the agent must infer the boundary itself.

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