pyfastmail-mcp

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

With no annotations provided, the description carries full burden for behavioral disclosure. It states the action ('Enable or disable') but doesn't mention permissions required, whether the change is reversible, rate limits, or what happens to emails sent to a disabled address. This leaves significant gaps 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 perfectly concise and well-structured. The first sentence states the core purpose, followed by a clear 'Args:' section with parameter explanations. Every sentence earns its place with zero waste.

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 2 parameters with 0% schema coverage and no annotations, the description adequately covers the basics but lacks behavioral context for a mutation tool. The existence of an output schema means return values don't need explanation, but permissions, side effects, and error cases remain undocumented.

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 explicitly documents both parameters: 'masked_email_id' as 'The ID of the masked email to update' and 'state' as 'New state: 'enabled' or 'disabled''. This adds crucial meaning beyond the bare schema, though it doesn't explain ID format or state implications.

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 verb ('Enable or disable') and resource ('a masked email address'), making the purpose immediately understandable. It doesn't distinguish from sibling tools like 'mail_create_masked_email' or 'mail_list_masked_emails', but the action is specific enough to understand what it does.

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 no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., needing an existing masked email), exclusions, or when to choose this over other mail tools like 'mail_manage_email_labels'. Usage context is implied but not explicit.

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