Zapmail MCP Server

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

No annotations are provided, so the description carries full burden for behavioral disclosure. While 'retrieves' implies a read-only operation, the description doesn't specify authentication requirements, rate limits, error conditions, or response format. The mention of 'endpoint' is generic and doesn't add meaningful behavioral context beyond what's implied by the verb.

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 extremely concise with just two short sentences. However, the second sentence 'Invoke this endpoint' is redundant and doesn't add value - it essentially repeats what the tool name and first sentence already imply. The description could be more efficient by removing this unnecessary instruction.

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 what the wallet balance represents (which currency, account, or context), how authentication works, what the response looks like, or which parameters are actually needed for this specific operation. The agent would struggle to use this tool effectively with only this minimal description.

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 thoroughly. The description adds no parameter information beyond what the schema provides - it doesn't explain which parameters are relevant for this specific wallet balance operation or provide usage examples. Baseline 3 is appropriate when the schema does all the parameter documentation work.

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 'retrieves the current wallet balance', which is a clear verb+resource combination. However, it doesn't distinguish this from sibling tools like 'wallet_balance' (which appears to be a similar tool) or other financial/account-related tools. The description is functional but lacks differentiation from alternatives.

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 doesn't mention any prerequisites, context requirements, or comparison to sibling tools like 'wallet_balance' or other balance/account tools. The agent receives no usage direction beyond the basic purpose statement.

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