Zapmail MCP Server

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

With no annotations provided, the description carries full burden. It discloses pagination behavior and the tool's purpose in a purchase workflow, which is helpful. However, it doesn't mention authentication requirements, rate limits, error conditions, or what 'eligible' specifically means beyond DNS Shield protection.

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 sized with three sentences that each add value: stating the core function, providing usage context, and including a call to action. It's front-loaded with the main purpose, though the final sentence 'Invoke this endpoint' is somewhat redundant.

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 read-only list tool with no annotations and no output schema, the description provides adequate but minimal context. It explains the purpose and pagination, but doesn't describe the return format, error handling, or authentication requirements that would be helpful given the complexity implied by 7 parameters.

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 what's in the schema. The baseline score of 3 reflects adequate coverage when the 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 specific action ('Retrieve a paginated list'), resource ('domains'), and qualification ('eligible for DNS Shield protection'). It distinguishes from siblings like 'get_available_domains' or 'retrieve_all_domains' by specifying the eligibility criteria for DNS Shield.

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 clear context for when to use this tool: 'before making a purchase' of DNS Shield protection. It implies this is a preparatory step, but does not explicitly state when not to use it or name specific alternatives among the many sibling tools.

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