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

Annotations are present: readOnlyHint=false, destructiveHint=false, indicating a non-destructive write operation. The description 'make an email template the account default' implies a change of state, which aligns with annotations. It adds no behavioral details beyond that, such as whether the previous default is replaced or if any permissions are needed, but given annotations cover basic safety, a mid score is appropriate.

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 a single sentence that is concise and to the point. It communicates the essential action without any fluff, which is ideal for a simple tool.

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?

With only one parameter and an output schema present, the description doesn't need to explain return values. It covers the action and scope. The only minor omission is explicit mention of when to use it (e.g., when wanting to change the default), but that is implied. For a simple tool, it is adequate.

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 coverage is 100%, so the parameter 'id' is well described as 'Template ID (from list_email_templates)', which is sufficient. The description doesn't add more, but with full schema coverage, a baseline of 3 applies. It earns a 4 because the schema description provides a clear reference for obtaining valid IDs, which is semantically rich.

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 the action ('set default') on a specific resource ('email template') with scope ('account default'). It is distinct from siblings like set_default_email_sender and list_email_templates, though it doesn't explicitly differentiate them.

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 when to use it: to set a default template for the account, but it doesn't explicitly mention alternatives or when not to use it. The sibling list includes set_default_email_sender, which might be confused, but the description clearly focuses on template, so usage context is fairly clear.

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