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

Annotations only declare readOnlyHint=false and destructiveHint=false; the description adds two substantive traits they don't cover: a rate limit of 10 attempts per minute and the authentication prerequisite. It omits failure behavior (invalid/expired code, lockout after the rate limit), which would be the natural next detail.

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?

Purpose is front-loaded in the first sentence, followed by the rate limit and then the access block. Every element earns its place, though the capitalized ACCESS block is comparatively verbose for the amount of new information it carries.

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 completion tool with no output schema, the description covers the auth path and the rate limit, which are the main operational unknowns. It leaves out code expiry and success/failure outcomes, a minor gap given the lack of a return schema.

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% and both parameters (code, session_id) are documented in the schema, so baseline is 3. The description adds nothing about code format or where session_id originates beyond the generic flow hint.

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?

States a specific verb and resource: submit a code to complete a 2FA challenge. This distinguishes it from start_2fa (which begins the flow) by using 'complete'. However, it never contrasts itself with the close siblings verify_2fa_magic_link or submit_verification_code, so an agent must infer the routing.

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?

Gives clear preconditions (a Proof account, an authenticated client or a start_login session) and the ordering constraint 'then call this tool again'. It does not mention alternatives such as wait_for_2fa or when not to use this tool, so it stops short of explicit routing.

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