Zapmail MCP Server

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

No annotations are provided, so the description must fully disclose behavioral traits. It states this is a purchase action with a one-time payment, implying a financial transaction and potential side effects like billing changes. However, it lacks details on authentication requirements, rate limits, error conditions, or what happens upon invocation (e.g., confirmation, immediate activation). The phrase 'Invoke this endpoint' is redundant and adds no behavioral insight.

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 and front-loaded, stating the core purpose in the first sentence. The second sentence adds useful context about LTD plans, and the third ('Invoke this endpoint.') is somewhat redundant but doesn't significantly bloat the text. Overall, it's efficiently structured with minimal waste.

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 purchase tool with no annotations and no output schema, the description is incomplete. It doesn't address critical aspects like required permissions, expected response format, error handling, or how it integrates with sibling tools. For a financial transaction tool, this lack of context could lead to incorrect agent usage, making it inadequate for safe operation.

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 7 parameters with 100% description coverage, so the schema documents each parameter's purpose (e.g., 'Override HTTP method', 'Override absolute API path'). The description adds no parameter-specific semantics beyond implying a purchase action, which doesn't clarify how parameters like 'method' or 'body' should be used for this tool. Given the high schema coverage, a baseline score of 3 is appropriate as the description doesn't compensate with additional param insights.

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 ('Purchase a Lifetime Deal') and resource ('DNS Shield plan'), specifying it's for a fixed number of domains with a one-time payment. However, it doesn't explicitly differentiate from sibling tools like 'purchase_dns_shield_25782088e0' or 'purchase_plan_25780426e0', which appear related but may have different scopes or payment models.

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. It mentions the tool's purpose but doesn't indicate prerequisites, such as needing an existing subscription or workspace, or when to choose this over other purchase-related tools in the sibling list. This leaves the agent without clear usage context.

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