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. While it mentions the destination system (Fastmail Files via WebDAV), it doesn't describe authentication requirements, rate limits, error conditions, whether overwrites occur, file size limits, or what happens on success/failure. For a file upload operation with zero annotation coverage, this leaves significant behavioral gaps.

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 efficiently structured with a clear purpose statement followed by parameter explanations. Every sentence adds value: the first establishes the core function, and the parameter explanations provide necessary context missing from the schema. There's zero wasted text or redundancy.

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 that this is a file upload operation with no annotations, 3 parameters (2 required), 0% schema description coverage, but with an output schema present, the description provides adequate basic information. The presence of an output schema means return values don't need explanation, but for a mutation tool with no safety annotations, more behavioral context would be helpful. It's minimally viable but has clear gaps.

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?

With 0% schema description coverage, the description provides essential parameter context that the schema lacks. It explains that 'path' is the destination path with an example, 'content' must be Base64-encoded, and 'content_type' has a default MIME type. This adds meaningful semantics beyond the bare schema, though it doesn't cover all potential parameter nuances like path format restrictions.

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 ('Upload a file') and target resource ('to Fastmail Files (WebDAV)'), distinguishing it from sibling tools like files_create_folder or files_move. It provides a complete verb+resource+system combination that leaves no ambiguity about what this tool 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 like mail_upload_attachment or files_create_folder. There's no mention of prerequisites, constraints, or typical use cases. The agent must infer usage context from the tool name and sibling list alone.

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