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 this is a list operation, implying it's read-only, but doesn't explicitly confirm safety, mention authentication requirements, rate limits, pagination behavior, or what happens if no mailboxes exist. The description provides basic functionality but lacks important operational context.

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 a single, efficient sentence that immediately communicates the core functionality. Every word contributes value by specifying both the action and the exact data fields returned. There's no wasted text or unnecessary elaboration.

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 simple read operation with zero parameters and an output schema exists, the description provides adequate context. It specifies what data fields are returned, which complements the output schema. For a straightforward list tool, this description is reasonably complete, though it could benefit from more behavioral context given the lack of annotations.

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 tool has zero parameters with 100% schema description coverage, so the baseline is 4. The description appropriately doesn't discuss parameters since none exist, and instead focuses on what the tool returns, which is valuable context for a parameterless operation.

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 ('List') and resource ('all mailboxes'), and specifies the fields returned (id, name, role, email counts, parentId). It distinguishes this as a listing operation rather than creation/deletion, but doesn't explicitly differentiate from other mail-related list tools like mail_list_identities or mail_list_masked_emails.

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 about when to use this tool versus alternatives. While the description implies it's for retrieving mailbox metadata, there's no mention of when to choose this over other mail tools or what context would trigger its use. The sibling tools include other list operations, but no comparisons are made.

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