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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the agent knows this is a safe read operation. The description adds the 'reusable' qualifier, which clarifies the scope of templates returned. It doesn't disclose pagination, ordering, or whether archived templates are included, but for a simple list tool with annotations covering safety, this is adequate.

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 sentence with no waste. The key qualifier 'reusable' is front-loaded and the sentence is immediately understandable.

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 zero-parameter list tool with an output schema present and annotations covering the safety profile, the description is nearly complete. It could mention whether the list is paginated or includes archived templates, but those are minor gaps given the tool's simplicity and the presence of an output 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?

The tool has zero parameters, so there is no schema burden to compensate for. The description's 'reusable' qualifier adds meaning about what kind of templates are listed, which is useful context beyond the empty schema. With 0 params, the baseline is 4, and the description meets it.

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 clear verb and resource: 'List reusable email templates.' It distinguishes from get_email_template (singular fetch) and create_email_template/update_email_template/delete_email_template (mutations). However, it doesn't explicitly differentiate from list_templates, which could be a broader listing of templates, so it's clear but not fully differentiated from that sibling.

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 implies usage: when you need a collection of reusable email templates. It doesn't explicitly state when to use this vs list_templates or get_email_template, nor any exclusions. The context is clear enough for a simple list tool, but no explicit routing guidance is given.

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