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 mentions the code has 'a limited validity period,' which adds useful context about temporal constraints. However, it fails to describe critical behaviors such as required permissions, rate limits, error conditions, or what the response looks like (since there's no output schema). For a tool that likely involves sensitive authentication data, this is a significant gap in transparency.

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 three sentences that avoid redundancy. It front-loads the core purpose and adds context about validity. However, the last sentence 'Invoke this endpoint' is unnecessary filler that doesn't add value, slightly reducing efficiency. Overall, it's well-structured but could be more tightly written.

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 authentication requirements, error handling, response format, and how to specify the mailbox. For a tool that retrieves sensitive codes, this leaves critical gaps for an agent to use it correctly and safely.

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 already documents all 7 parameters with descriptions. The description does not add any parameter-specific semantics beyond what the schema provides (e.g., it doesn't clarify which parameters are needed for this specific endpoint). Given the high schema coverage, the baseline score of 3 is appropriate, as the description offers no extra parameter 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 states the tool 'retrieve[s] an authenticator code for a specific mailbox' and mentions its use for authentication with limited validity. This provides a clear verb ('retrieve') and resource ('authenticator code'), but it does not distinguish this tool from siblings (e.g., no mention of how it differs from other authentication-related tools in the list). The purpose is somewhat vague as it lacks specifics on what the code is used for beyond 'authentication purposes'.

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 does not mention prerequisites (e.g., needing a mailbox ID), exclusions, or sibling tools. The phrase 'Invoke this endpoint' is generic and adds no contextual usage information. Without any when-to-use or when-not-to-use cues, the agent must infer usage from the tool name alone.

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