Apple Mail MCP Server

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

With no annotations provided, the description carries full behavioral disclosure burden. It explains the fallback logic between text_body and html_body parameters, default behaviors for open_in_mail (True) and save_as_draft (False), and the file generation mechanism. Minor gap: does not specify file overwrite behavior or error conditions when output_path exists.

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?

Excellent structure with four distinct sections (purpose/rationale, Args, Returns). Information density is high with zero waste—every sentence provides actionable guidance (e.g., explaining why .eml is preferred) or parameter constraints. Technical details (comma-separated, fallback generation) are precisely where needed.

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?

Given 10 parameters with complex interdependencies (text_body/html_body fallbacks) and 0% schema coverage, the description is remarkably complete. It documents all parameters, explains return structure ('Confirmation with the generated `.eml` path'), and covers the output schema existence. No gaps remain for agent invocation decisions.

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% (titles only), requiring full compensation. The Args section provides rich semantics for all 10 parameters: account includes examples ('Work', 'Oracle'), recipient fields specify comma-separated formatting, body fields explain mutual fallback generation, and booleans clarify default values. Comprehensive coverage of complex parameter interactions.

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?

Description explicitly states the tool generates unsent `.eml` messages for rich-text emails, using specific verbs (create/generate) and resource identifiers. It clearly distinguishes itself from sibling `compose_email` by explaining this is the 'preferred path for HTML or richly formatted emails because Mail reliably renders `.eml` content, while setting raw HTML through AppleScript often stores the literal markup instead.'

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?

Provides explicit when-to-use guidance by contrasting with AppleScript alternatives: 'This is the preferred path for HTML or richly formatted emails.' It explains the technical rationale (reliable rendering vs. literal markup storage), giving agents clear criteria for selecting this tool over `compose_email` or other siblings.

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