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

With no annotations, the description carries the full behavioral disclosure burden. It discloses that the link is emailed and not returned, but it directly conflicts with the schema's note that in the current no-SMTP setup the link may be returned. It also omits expiration, rate-limit, and idempotency behavior, so the agent receives partially misleading behavioral information.

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 a single tight sentence with the core action front-loaded and the important 'not returned here' caveat placed immediately. The mention of the `verify` step earns its place by providing necessary flow context with no filler.

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?

This is a simple one-parameter tool, and the description covers the main flow and names the next step. However, it fails to reflect the no-SMTP return behavior mentioned in the schema and leaves out practical details like link expiration or error behavior, so the agent's understanding is incomplete.

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% and the email parameter is already well described, including the no-SMTP caveat. The description adds no parameter-level meaning beyond restating that the link is for that email, so the baseline score 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?

The description uses a specific verb and resource — 'Request a magic sign-in link for an email' — and clearly distinguishes this from the sibling `verify` tool by naming it as the follow-up step. An agent can tell exactly what this tool does without opening the 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?

It gives a clear procedural context: request the link, retrieve the token from email, then pass it to `verify` to complete sign-in. It does not explicitly state when *not* to use this tool or compare it with alternatives, but the named flow is sufficient guidance for the intended usage.

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