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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so the safety profile is covered without description help. The description adds only the lookup modes (built-in type vs custom template key); it says nothing about behavior on an unknown key, permission requirements, or returned shape.

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 efficient sentence with the verb front-loaded and no filler. It is concise to a fault, but nothing in it is wasted.

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 2-parameter tool with 0% schema description coverage and no output schema, the description is too thin: it omits the request_id parameter, the key format, and any failure behavior. An agent can attempt a call but cannot confidently construct correct inputs from the description alone.

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 0%, so the description must carry the parameter burden. It hints that email_type accepts a built-in type or custom template key, but never explains the naming format or pattern constraint, and the second parameter (request_id) is not mentioned at all.

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 names a verb ('Read') and resource ('an email'), but the resource is ambiguous: the tool name and siblings say 'email_templates', yet the text says 'email'. The phrase 'by built-in type or custom template key' partially resolves this to templates, but an agent must infer the distinction from email_templates_list/preview rather than being told.

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?

There is no explicit when-to-use guidance and no alternative named, despite a dense cluster of siblings (email_templates_list, email_templates_preview, email_templates_preview_customization) that an agent could easily confuse with this one. Usage is only weakly implied by 'Read ... by ... key'.

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