Zapmail MCP Server

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 tool cancels subscriptions 'immediately', which is useful behavioral context. However, it lacks details on permissions required, whether cancellation is reversible, refund policies, or what happens to associated resources (e.g., domains, mailboxes). For a destructive operation with zero annotation coverage, this is insufficient.

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 brief and front-loaded with the core action, but the second sentence ('Invoke this endpoint.') is redundant and adds no value. Otherwise, it's efficiently structured with two substantive sentences.

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 destructive tool with no annotations and no output schema, the description is incomplete. It doesn't explain what 'cancel' entails (e.g., immediate termination, prorated charges), what data is returned, or error conditions. Given the complexity and lack of structured data, more context is needed for safe use.

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 100%, so the schema fully documents all 7 parameters. The description adds no parameter-specific information beyond implying a subscription identifier might be needed (though not stated). With high schema coverage, the baseline is 3, as the description doesn't compensate but doesn't detract either.

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 ('Cancel') and resource ('DNS Shield subscription'), specifying it works for both Monthly and Lifetime Deal plans. However, it doesn't distinguish from sibling 'cancel_subscription_13489478e0', which appears to be a similar tool, leaving some ambiguity about when to use one versus the other.

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, prerequisites, or exclusions. It mentions applicability to Monthly and LTD plans but doesn't clarify if there are other subscription types or contexts where it shouldn't be used.

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