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

No annotations are provided, so the description carries the burden. It discloses the access requirement (needs a Proof account), the authentication flow, and the fact that no code submission is involved. However, it does not mention side effects such as token consumption, session activation after success, or error/timeout behavior, leaving some ambiguity about what happens on completion.

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 front-loaded: the first paragraph states the purpose and key distinction, and the second paragraph covers access prerequisites and the invocation flow. Every sentence adds value, though it is slightly less lean than a two-sentence ideal.

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 single-parameter tool with no output schema and no annotations, the description covers the essential operational context: token origin, proof mechanism, access requirements, and the necessary prerequisite login step. It doesn't specify return values or failure handling, but these are less critical for this simple completion action.

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 parameter is already described as 'Magic link token from the verification email.' The description adds emphasis that the token itself is the proof, but this is more contextual reinforcement than new parameter semantics, so the baseline of 3 applies.

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 states a specific action—'Complete a 2FA challenge'—using a magic link token, and explicitly contrasts it with code submission: 'No code submission needed—the token itself is the proof.' This clearly distinguishes the tool from siblings like verify_2fa and submit_verification_code.

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 provides clear context for when to use the tool: when a magic link token was received via email, no code is needed. It also gives explicit access prerequisites and an alternative login flow by naming start_login. However, it does not explicitly name the code-based sibling alternatives, so the when-not is somewhat implied rather than fully explicit.

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