list_templates

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

Annotations already provide readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds context beyond that by explaining the template storage location (files in ~/.apple_mail_mcp/templates/) and the environment variable override, as well as the exact return structure (name and subject, with null when no subject header). This enriches the behavioral understanding without contradicting 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 multi-paragraph but every part carries useful information: the purpose, the file storage location, the environment override, and the return format. It is front-loaded with the core purpose. It could be trimmed slightly, but the extra context is valuable and not redundant for a tool with no parameters.

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, read-only, idempotent operation with an output schema present, the description covers everything an agent needs: the action, the storage source, the return shape, and the environment override. There is no missing element that would prevent correct invocation.

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, and the schema defines no properties, so the description cannot add parameter details. However, it does mention the APPLE_MAIL_MCP_HOME environment variable, which influences behavior but is not a tool parameter. With no parameters to document, the description appropriately need not compensate for schema gaps, making the baseline 4 a fair score.

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 first line 'List all stored email templates' clearly states the action (list) and resource (email templates), distinguishing it from sibling tools like get_template (single retrieval) or save_template (creation). The additional context about file location reinforces the scope without confusion.

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 does not explicitly guide when to use this tool versus alternatives such as get_template or render_template. It relies on the verb 'list all' to imply broad retrieval, but it never states usage conditions, exclusions, or preferred scenarios. Given the numerous template-related siblings, explicit routing would improve clarity.

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