Zapmail MCP Server

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

With no annotations, the description carries full burden but only states it 'lets you fetch a list,' implying a read operation. It lacks critical behavioral details: whether it's paginated, requires authentication, has rate limits, returns structured data, or handles errors. This is inadequate for a tool with 7 parameters and no output schema.

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 two sentences, but the second ('Invoke this endpoint.') is redundant and adds no value. It's front-loaded with the core purpose, though it could be more structured by integrating parameter hints.

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 7 parameters, no annotations, and no output schema, the description is incomplete. It doesn't address return values, error handling, or behavioral constraints, leaving significant gaps for an agent to understand how to use this tool effectively in context.

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 parameters are documented in the schema. The description adds no meaning beyond implying a fetch operation, but it doesn't explain how parameters like 'method' or 'serviceProvider' relate to retrieving mailboxes. Baseline 3 is appropriate as 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 states the tool 'fetch[es] a list of all mailboxes,' which clarifies the verb (fetch/list) and resource (mailboxes). However, it's vague about scope (e.g., all mailboxes in what context?) and doesn't differentiate from sibling tools like 'search_mailboxes' or 'get_mailbox_details_by_id_13490215e0,' leaving ambiguity in purpose.

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?

No guidance is provided on when to use this tool versus alternatives. It doesn't mention prerequisites, context (e.g., workspace or domain filtering), or compare to siblings like 'search_mailboxes' or 'retrieve_all_domains_13520015e0,' offering no help in selection.

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