pyfastmail-mcp

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

With no annotations provided, the description carries the full burden. It discloses the destructive nature (moving to Trash or permanent destruction) and the default behavior (moves to Trash if permanent is false). However, it lacks details on permissions needed, rate limits, or what happens if email_ids are invalid, leaving behavioral gaps.

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 front-loaded with the core purpose in the first sentence, followed by a concise Args section. Every sentence adds value without redundancy, making it efficient and well-structured for quick understanding.

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 tool's complexity (destructive operation with 2 parameters), no annotations, and an output schema (which handles return values), the description is mostly complete. It covers the purpose, parameters, and behavior but could improve by addressing error cases or permissions, though the output schema mitigates some gaps.

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%, so the description must compensate. It explains email_ids as 'List of JMAP email IDs to delete' and permanent as controlling destruction vs. Trash, adding meaning beyond the schema's basic types. However, it does not detail the format of JMAP IDs or the implications of permanent deletion, leaving some semantics unclear.

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 ('Delete one or more emails') and specifies the mechanism ('by moving to Trash, or permanently destroy them'). It distinguishes from sibling tools like mail_archive_email or mail_move_email by focusing on deletion rather than archiving or relocating.

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 clear context for when to use this tool (to delete emails) and implies when not to use it (e.g., for archiving or moving emails, as indicated by sibling tools). However, it does not explicitly name alternatives or specify prerequisites, such as requiring email IDs from prior operations.

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