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 of behavioral disclosure. It states 'Cancel a user subscription,' implying a destructive mutation, but fails to detail critical aspects like required permissions, whether the cancellation is immediate or pending, refund policies, or error handling. This leaves significant gaps in understanding the tool's behavior.

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 concise with two sentences, front-loading the main action ('Cancel a user subscription') and avoiding unnecessary details. However, the second sentence ('Invoke this endpoint.') is somewhat redundant and could be omitted without losing clarity, slightly reducing efficiency.

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 complexity of a cancellation tool with 7 parameters, no annotations, and no output schema, the description is insufficient. It lacks details on behavioral traits, parameter usage, and expected outcomes, making it incomplete for safe and effective tool invocation in this context.

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 description mentions 'by providing its subscription ID,' which hints at a parameter, but the input schema has 7 parameters with 100% coverage, including 'method,' 'path,' and others not related to subscription ID. The description does not add meaningful semantics beyond the schema, such as explaining how parameters interact or their relevance to cancellation, so it meets the baseline for high schema coverage.

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 verb ('Cancel') and resource ('a user subscription'), making the purpose specific and understandable. However, it does not explicitly differentiate from sibling tools like 'cancel_subscription_25783127e0' or 'remove_mailboxes_on_next_renewal_13490521e0', which might handle similar cancellation actions, so it 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?

The description provides no guidance on when to use this tool versus alternatives, such as other cancellation-related siblings or tools for modifying subscriptions. It mentions 'Invoke this endpoint,' but this is generic and does not offer context-specific usage instructions or exclusions.

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