Zapmail MCP Server

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

With no annotations provided, the description lacks critical behavioral details. It doesn't specify whether this is a read-only operation, what permissions are required, if there are rate limits, or how results are returned (e.g., pagination). The mention of filtering is helpful but insufficient for a tool with 7 parameters.

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 brief and front-loaded with the core purpose, though the final sentence 'Invoke this endpoint' is redundant. It efficiently conveys the main idea in two sentences 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?

For a tool with 7 parameters, no annotations, and no output schema, the description is inadequate. It doesn't explain the return format, error conditions, or behavioral expectations, leaving significant gaps for an AI agent to understand how to use it effectively.

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 minimal value by mentioning filtering by 'status, tags, and search terms', which loosely maps to some query parameters but doesn't provide additional syntax or format details beyond the schema.

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 ('Retrieve a list') and resource ('mailboxes eligible for placement testing'), making the purpose understandable. It distinguishes from siblings like 'retrieve_all_mailboxes' by specifying eligibility for placement tests, though it doesn't explicitly contrast with other mailbox-related tools.

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 mentions filtering capabilities but provides no guidance on when to use this tool versus alternatives like 'retrieve_all_mailboxes' or 'search_mailboxes'. There are no explicit instructions on prerequisites, context, or exclusions for usage.

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