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

Annotations declare readOnlyHint false and destructiveHint true, so the description must clarify the mutating nature. It does so by describing the creation/access flow and that a fresh API key is returned even for existing accounts. It also details the authentication message format and timestamp freshness constraint (5 minutes), adding meaningful behavioral context. It does not contradict the annotations, and the added details about the signing process and error codes (validation, signature_failed, rate_limited) enhance transparency.

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?

The description is well-structured with a clear intro paragraph, then Args and Returns sections. While it is fairly long, every sentence adds necessary information (message format, timestamp constraint, key usage, error handling). It is front-loaded with the core purpose and usage context, then details. No filler or redundancy; it earns its length.

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?

Given the complexity of a wallet-signature authentication flow, the description is remarkably complete. It covers the exact message to sign, parameter constraints, return values including api_key and key_prefix, error codes, and post-call usage (Bearer token, configure_api_key, _meta). The output schema is not provided, so the description's Returns section is the sole source for return format, and it is thorough. Nothing essential for an agent to call the tool correctly 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% with each parameter briefly described, but the description adds critical semantics beyond the schema: it specifies the exact message to sign, the timestamp must be within the last 5 minutes, and the signature is EIP-191 personal_sign. This is essential for correct invocation and goes beyond the schema's one-line descriptions. The description also explains the relationship between timestamp and the signed message, which the schema alone does not convey.

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 clearly states the purpose: 'Create (or access) a Maginary account using a wallet signature.' It specifies the resource (account) and the method (wallet signature), and distinguishes itself from the sibling 'create_account' by noting the email-less workflow. The phrase 'Create (or access)' clarifies that it handles both new and existing accounts, which is precise and unambiguous.

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?

The description explicitly provides usage context: 'Use this when you have a wallet but no email.' This signals the alternative (create_account for email users) and gives a clear decision rule. It also explains how to use the returned api_key via multiple channels, which guides the agent on subsequent actions. This is comprehensive and leaves no ambiguity about when to invoke this tool.

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