Zapmail MCP Server

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

No annotations are provided, so the description carries the full burden. It states the tool fetches data, implying a read-only operation, but doesn't disclose critical behavioral traits like authentication requirements, rate limits, error handling, or response format. The mention of 'Invoke this endpoint' is vague and adds no practical context, leaving significant gaps in understanding how the tool behaves.

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 front-loaded with the core purpose in the first sentence, followed by a less informative second sentence ('Invoke this endpoint') that adds minimal value. It's appropriately sized but could be more efficient by omitting the redundant second part, keeping it to one clear sentence.

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 the tool's complexity (7 parameters, no annotations, no output schema), the description is incomplete. It fails to address behavioral aspects like authentication, response structure, or error cases, which are crucial for a tool that fetches user data. Without annotations or output schema, the description should provide more context to guide effective use, but it falls short.

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 input schema has 100% description coverage, documenting all 7 parameters with their types and purposes. The description adds no parameter-specific information beyond what the schema provides, such as explaining how parameters like 'method' or 'workspaceKey' relate to fetching subscriptions. With high schema coverage, the baseline score of 3 is appropriate, as the description doesn't compensate but also doesn't detract.

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 action ('Fetch') and resource ('all subscriptions associated with the authenticated user'), including scope details like statuses (active, cancelled, expired) and included data (plan and billing details). It distinguishes from siblings by specifying it retrieves all subscriptions for the user, unlike tools like 'cancel_subscription_13489478e0' or 'get_subscriptions_25778521e0' which might have different scopes, though it doesn't explicitly differentiate from similarly named siblings.

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, such as other subscription-related tools in the sibling list (e.g., 'get_subscriptions_25778521e0', 'cancel_subscription_13489478e0'). It mentions invoking the endpoint but lacks context on prerequisites, timing, or exclusions, leaving the agent with no usage direction.

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