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

With no annotations provided, the description carries the full behavioral disclosure burden. It reveals a useful rate limit (10 attempts per minute) and an access prerequisite (Proof account, session from start_login), which go beyond the schema. It does not describe failure modes, code consumption, or return values, but it does disclose two important behavioral constraints.

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 compact and action-first, with no filler. The rate-limit and access instructions are each purposeful, and the structure makes it easy to scan quickly.

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 two-parameter tool with no output schema, the description covers the main non-obvious constraints (rate limit, authentication prerequisite) and provides a mapping to start_login. It omits any information about the response or what a successful/failed verification returns, so a callable agent is not fully briefed on outcomes.

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%: both code and session_id are already described in the input schema. The description adds no parameter-level details, so 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?

The description clearly states a specific action ('Submit a verification code') and its goal ('complete a 2FA challenge'), making the tool's purpose unmistakable. However, it does not differentiate from the sibling tool submit_verification_code, which appears to do nearly the same thing, nor does it clarify the relationship with verify_2fa_magic_link.

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 usage guidance: a Proof account is required, and the agent should authenticate this client or sign in via start_login to obtain a session before calling verify_2fa. It does not explicitly name alternative tools or state when NOT to use this tool, but the access workflow is clear.

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