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

Annotations already establish that this is a non-read-only, non-idempotent, non-destructive mutation. The description adds no behavioral context beyond the verb 'Attaches' – it does not clarify whether an existing email is replaced, whether duplicates are allowed, or what side effects occur.

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?

A single short sentence with the action and object front-loaded. It contains no redundant or filler content, and every word contributes to understanding the tool's purpose.

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 simple two-parameter mutation with an output schema and helpful annotations, the description is minimally viable. It covers the core purpose and parameters, but it lacks guidance on duplicate or replacement email behavior, which would help an agent know what to expect when invoking the tool.

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 are already documented with formats and provenance (subjectId from a prior call). The prose description adds no additional semantic detail, so the schema 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 ('Attaches') and a specific resource ('an email address to an SMI subject'), which clearly differentiates it from the many sibling smi_add_subject_* tools by the type of data being attached.

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 intended use is implied by the resource name: use this tool when an email needs to be attached to an SMI subject. However, the description does not explicitly state when to prefer this over alternatives or mention prerequisites such as obtaining a valid subjectId, which is left entirely to the parameter schema.

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