otp_send_email

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

Annotations provide readOnlyHint=false and destructiveHint=false, but the description adds critical behavioral details: the mandatory placeholder requirement, the explicit error condition (422), and default values for expiry and length. This goes well beyond the annotations.

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 somewhat verbose but well-structured: it opens with a critical warning, then lists parameters in a consistent format. Every sentence provides value, though a slight reduction in length could improve conciseness.

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?

Given the tool's 5 parameters (3 required), the presence of an output schema, and no nested objects, the description covers all necessary behavioral aspects: failure conditions, defaults, and parameter constraints. It is complete enough for an AI agent to select and invoke correctly.

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?

While the schema already covers 100% of parameters, the description enriches understanding by emphasizing the critical placeholder requirement for the message parameter, providing an example, and clarifying default values. This adds significant meaning beyond the schema.

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 'Send an OTP (One-Time Password) via Email,' which is a specific verb+resource combination. The tool name itself distinguishes it from siblings like otp_send_sms and otp_verify_email, and the description reinforces this by specifying the email channel.

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 explicitly warns that the message parameter must contain <%otp_code%> or the call will fail with a 422 error. However, it does not explicitly state when to use this tool versus alternative OTP delivery methods (e.g., SMS). The context from sibling tool names implies the distinction, but explicit guidance would improve score.

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