Zapmail MCP Server

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It describes a read operation ('retrieve') and aggregation, but fails to mention critical details like authentication requirements, rate limits, error handling, or the format of the returned summary. For a tool with 7 parameters and no output schema, this omission is significant and leaves the agent with incomplete behavioral understanding.

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 are front-loaded: the first states the purpose, the second elaborates on scope and insights, and the third is a call to action. There is minimal waste, though the third sentence ('Invoke this endpoint.') is somewhat redundant and could be omitted for better 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 (7 parameters, no annotations, no output schema), the description is incomplete. It lacks details on behavioral traits, output format, and usage context. While the schema covers parameters, the description does not compensate for the missing annotations and output schema, leaving gaps in understanding how to effectively use this tool.

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 100% description coverage, so the schema already documents all 7 parameters thoroughly. The description adds no additional meaning about parameters, such as explaining which ones are essential for the report or how they affect the aggregation. This meets the baseline score of 3, as the schema does the heavy lifting without description enhancement.

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: 'Retrieve an overall summary of all placement test results' and 'aggregates data across all your placement tests, providing insights into email deliverability performance across different providers and mailboxes.' It specifies the verb ('retrieve'), resource ('overall summary of all placement test results'), and scope ('across all your placement tests'). However, it doesn't explicitly differentiate from sibling tools like 'get_placement_test_orders_25779469e0' or 'get_available_placement_test_credits_25779804e0', which prevents a perfect score.

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 'invoke this endpoint' but offers no context about prerequisites, timing, or comparison to sibling tools such as those for specific placement test orders or credits. This lack of explicit usage instructions or exclusions limits its helpfulness for an AI agent.

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