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 implies a write operation ('Create'), it doesn't mention authentication requirements, error conditions, rate limits, or what happens on success (e.g., returns event ID). The description is insufficient for a mutation tool with zero annotation coverage.

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 sentence followed by a well-organized Args section. Every sentence adds value, though the calendar_href reference could be more integrated into the main description rather than parenthetical.

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?

For a 7-parameter mutation tool with no annotations, the description covers parameters well but lacks behavioral context. The existence of an output schema reduces the need to describe return values, but critical details like authentication, error handling, and success behavior 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?

With 0% schema description coverage, the description compensates well by explaining all 7 parameters in the Args section, including format details for start/end (ISO strings), optional defaults, and all_day behavior. It adds significant value beyond the bare schema, though it could explain calendar_href sourcing more clearly.

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 ('Create a new event') and resource ('in a CalDAV calendar'), distinguishing it from siblings like calendar_update_event or calendar_delete_event. The first sentence provides a complete, unambiguous purpose statement.

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 calendar_update_event, nor does it mention prerequisites (e.g., needing calendar_href from calendar_list_calendars as context). The Args section documents parameters but doesn't offer usage context.

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