pyfastmail-mcp

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

With no annotations provided, the description carries full burden. It mentions 'preserving the original content' and auto-selection behavior for identity_id, but fails to disclose critical behavioral traits such as whether this is a mutating operation, permission requirements, rate limits, error conditions, or what the output contains. The description is insufficient for a mutation tool.

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 well-structured with a clear purpose statement followed by parameter explanations. Every sentence adds value, though the parameter section could be slightly more concise. It's appropriately sized for a 4-parameter tool.

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 this is a mutation tool with no annotations but with an output schema (which handles return values), the description is moderately complete. It covers parameters well but lacks behavioral context about the operation's effects, permissions, or error handling. The presence of output schema prevents a lower score.

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 provides clear semantic explanations for all 4 parameters: email_id identifies the source, to specifies recipients, text_body adds optional introductory text, and identity_id controls sender identity with auto-selection behavior. This adds substantial value beyond the bare 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 specific action ('Forward an email'), target resource ('an email'), and key behavior ('preserving the original content'). It distinguishes itself from sibling tools like mail_send_email (new email) and mail_reply_to_email (reply to sender).

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 context through the parameter explanations (e.g., 'auto-selects first if omitted' for identity_id), but lacks explicit guidance on when to use this tool versus alternatives like mail_send_email or mail_reply_to_email. No prerequisites or exclusions are mentioned.

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