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

Annotations only provide coarse flags (openWorldHint true, readOnlyHint false), so the description carries the behavioral burden. It discloses an unusual behavioral trait: the server does not adopt the minted tokens as the session credential and they must be returned to the operator. The explicit no-logging and no-repeating rules add security-relevant behavior beyond the annotations.

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?

Every sentence earns its place: purpose, provider strategy, exclusions, token handling, and security constraints. The description is dense but not bloated, and the most important routing information is front-loaded.

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 multi-provider auth tool with no output schema, the description covers the provider matrix, prerequisite tools, security handling, and operator handoff well. It does not describe exact response fields, error cases, or when to prefer refreshToken, but these are secondary to the core login flow.

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%, but the description adds value by mapping providers to their required parameter combinations: siwe uses message+signature, email_otp uses email+otp, and phone_otp uses phone+otp. It also identifies the source tools for those credentials, which the bare schema properties do not provide.

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 opens with a specific verb and resource: 'Authenticate and receive an access/refresh token pair.' It also enumerates accepted providers and explicitly excludes browser ceremonies, so an agent can tell what login produces and what it is not.

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 gives concrete when-to-use guidance: siwe is 'preferred for dedicated agents that can sign', while email_otp and phone_otp are tied to their prerequisite tools. It also states what not to use (Passkey, Privy, SSO) and what to do with the result. It does not contrast login with the sibling refreshToken, but the core selection guidance is explicit.

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