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 this is a purchase action with a one-time payment, implying a financial transaction and system change. However, it lacks critical behavioral details: required permissions, whether this creates a new subscription or modifies an existing one, confirmation steps, error conditions, or what happens after invocation (e.g., domain allocation). The phrase 'Invoke this endpoint' is generic and unhelpful.

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 appropriately concise with three sentences. The first sentence states the core action, the second explains LTD benefits, and the third is a generic call-to-action. While efficient, the third sentence ('Invoke this endpoint.') adds no value and could be removed without loss.

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 purchase tool with 7 parameters, no annotations, and no output schema, the description is incomplete. It lacks essential context: what specific plan options exist, how domains are specified/allocated, payment requirements, success/error responses, and how this integrates with sibling tools (e.g., allocation tools). The agent must infer too much from minimal information.

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 purchase action. It doesn't explain what data should go in body/pathParams/query for this specific endpoint, leaving the agent to guess based on generic parameter descriptions. Baseline 3 is appropriate when schema does the heavy lifting.

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 tool's purpose: purchasing a Lifetime Deal DNS Shield plan with a one-time payment. It specifies the resource (DNS Shield plan) and key characteristics (LTD, one-time payment, fixed domains). However, it doesn't explicitly differentiate from sibling tools like 'purchase_subscription_25771049e0' or 'upgrade_dns_shield_ltd_plan_25782123e0', which appear related.

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 LTD plans but doesn't explain when to choose this over other purchase tools (e.g., 'purchase_subscription_25771049e0') or how it relates to 'upgrade_dns_shield_ltd_plan_25782123e0'. No prerequisites, exclusions, or contextual triggers are specified.

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