pyfastmail-mcp

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

No annotations are provided, so the description carries full burden. It states the action ('Download') but doesn't disclose behavioral traits like authentication requirements, rate limits, whether it's a read-only operation, what happens on failure, or the output format. The description is minimal and lacks critical behavioral context for a download operation.

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 appropriately sized and front-loaded: the first sentence states the purpose, followed by a structured 'Args:' section. Every sentence earns its place, with no redundant information. It could be slightly more concise by integrating the args into the main text, but it's well-structured.

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 3 parameters with 0% schema coverage and no annotations, but with an output schema present, the description is moderately complete. It covers parameter semantics adequately but lacks behavioral context (e.g., permissions, errors). The output schema likely handles return values, so the description doesn't need to explain those, but overall completeness is limited for a download 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 adds meaning by explaining each parameter's purpose: 'blob_id' is from 'email attachments list', 'name' is 'the filename to use for the download', and 'content_type' is 'MIME type' with a default. This clarifies semantics beyond the bare schema, but doesn't fully compensate for the coverage gap (e.g., no format examples or constraints).

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 tool's purpose: 'Download an attachment blob by blobId.' It specifies the verb ('Download') and resource ('attachment blob'), but doesn't differentiate from sibling tools like 'mail_upload_attachment' or explain what distinguishes downloading from other mail operations. The purpose is clear but lacks sibling differentiation.

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. The description doesn't mention prerequisites (e.g., needing an attachment list first), when not to use it, or how it relates to sibling tools like 'mail_get_email' or 'mail_upload_attachment'. 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.