Apple Mail MCP Server

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

With no annotations provided, the description carries the full burden. It successfully discloses the send/draft/open modes and their interactions (mode overrides send), reply_to_all behavior, and HTML/plain text fallback requirements. However, it lacks disclosure of error behaviors (e.g., multiple subject matches), authentication requirements, or rate limits.

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 docstring format (Args/Returns) is well-structured and front-loaded with the core purpose. While lengthy due to the need to document 10 undocumented parameters, every sentence provides necessary value given the schema coverage gap. Minor verbosity in the Returns section.

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 10-parameter tool with complex delivery modes and no annotations, the description is comprehensive. It covers all parameters, return values, and the critical mode/send interaction. Minor gaps remain regarding edge cases (multiple email matches) and authorization requirements.

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?

Given 0% schema description coverage, the Args section comprehensively compensates by documenting all 10 parameters with rich semantics, including format examples (account: 'Gmail', 'Work'), delimiter specifications (comma-separated for cc/bcc/attachments), and path examples for attachments.

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 opening sentence 'Reply to an email matching a subject keyword' provides a specific verb (Reply), resource (email), and distinguishing mechanism (subject keyword search) that clearly differentiates it from sibling tools like compose_email (new emails) and forward_email (forwarding).

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 provides no explicit guidance on when to use this tool versus alternatives like compose_email or forward_email, nor does it mention prerequisites (e.g., that the target email must exist). The agent must infer usage solely from the parameter names.

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