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

With no annotations provided, the description carries the full behavioral burden. It discloses the 400 unsupported_for_type error for unsupported pairs, the authentication prerequisite, and the fact that start_login does not open this tool. It does not explicitly state that submission is a mutating action, but that is implied. It also doesn't describe the success response, but that is not required. Overall, it is quite transparent about constraints and prerequisites.

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 dense and efficient, with no filler. It leads with the core purpose, then immediately states the strict acceptance criteria, then lists alternatives, and finally the access requirement. Every sentence earns its place and the structure is logical, making it easy for an agent to parse.

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 tool with no output schema, the description covers all essential aspects: supported inputs, error conditions, alternatives, and authentication. An agent can correctly determine when to call this tool and what to expect. Nothing critical is missing.

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?

The input schema already provides descriptions for both parameters (id and code) at 100% coverage. The tool description does not add any additional parameter-level semantics beyond what the schema states, so it does not improve on the baseline of 3.

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 verb ('Submit') and resource ('OTP/challenge code for a pending verification'), and immediately specifies the supported type/channel pairs. It explicitly distinguishes itself from other verification completion methods (trigger_verification, phone, social, telegram_bot), leaving no ambiguity about what it does.

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 provides explicit when-to-use and when-not-to-use guidance, naming the exact conditions (type 'email', and type 'domain' with channel 'email') and listing alternative tools for other cases. It also clarifies that start_login does not open this tool, and that authentication is required. This is exemplary routing.

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