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 adds valuable behavioral context about thread matching ('same or similar subject') and return formatting ('sorted by date'). However, it omits safety characteristics (read-only status, error handling if thread not found) that would be necessary for complete transparency without 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 docstring format with Args and Returns sections is well-structured and front-loaded. Each parameter description earns its place by providing examples or constraints. The format is slightly formal but efficiently organized without redundant prose.

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 the 4 parameters with zero schema descriptions, the description successfully documents all inputs and the return value ('Formatted thread view'). It adequately covers the tool's contract despite lacking annotations, though it could improve by explicitly stating the read-only nature of the operation.

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 input schema has 0% description coverage (titles only). The description fully compensates by documenting all 4 parameters with clear semantics, practical examples ('Gmail', 'Re: Project Update'), and explicit default values ('default: 50', 'default: INBOX'). This adds essential meaning missing from the structured schema.

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 tool 'Get[s] an email conversation thread' and specifies the scope as 'all messages with the same or similar subject,' which distinguishes it from siblings like search_emails (broad search) or list_inbox_emails (general listing). The verb and resource are specific and unambiguous.

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 usage through the specific mention of 'conversation thread' and 'subject_keyword,' suggesting when to use this versus general search tools. However, it lacks explicit guidance on when to prefer this over search_emails or get_inbox_overview, and does not mention prerequisites or exclusions.

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