pyfastmail-mcp

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

With no annotations provided, the description carries full burden but provides minimal behavioral context. It states the action but doesn't disclose whether this requires specific permissions, if changes are reversible, rate limits, error conditions (e.g., invalid email IDs), or what happens to emails already in the target state. For a mutation tool with zero annotation coverage, this is inadequate.

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?

Perfectly concise and well-structured. The first sentence states the purpose, followed by a clear 'Args:' section with bullet-point explanations. Every sentence earns its place with zero wasted words, and the most important information (what the tool does) is front-loaded.

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 moderate complexity (mutation with 2 parameters), no annotations, and an output schema present (which reduces need to describe return values), the description is partially complete. It covers the basic action and parameters but lacks behavioral context (permissions, side effects) and usage guidance. The presence of an output schema helps, but the description should do more for a mutation tool.

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 clearly explains both parameters: 'email_ids' as 'List of JMAP email IDs to update' and 'read' as 'True to mark as read, False to mark as unread (default True)'. This adds essential meaning beyond the bare schema, though it doesn't specify format details for JMAP IDs or handling of empty lists.

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 specific action ('Set or unset the $seen flag') on specific resources ('one or more emails'), using precise terminology. It distinguishes itself from sibling mail tools like mail_archive_email or mail_move_email by focusing on read/unread status manipulation rather than archiving, moving, or other email operations.

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?

No guidance is provided on when to use this tool versus alternatives. While the purpose is clear, there's no mention of prerequisites (e.g., needing email IDs first), comparison to similar tools (e.g., mail_manage_email_labels for other flag changes), or typical use cases (e.g., batch updates after viewing emails).

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