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. It discloses that the tool returns a Stripe checkout session link, which hints at a read-only operation (since it 'returns' something), but it does not clarify authentication needs, rate limits, side effects, or error handling. The description is minimal and lacks behavioral details beyond the basic output, leaving significant gaps 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 a single sentence that is front-loaded with the tool's purpose, but it includes an unnecessary markdown link and lacks structure. It is concise in length but could be more efficient by omitting the link and focusing on clarity. The sentence earns its place by stating the action, but the mismatch with the tool name reduces its effectiveness.

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 explains what the tool does at a high level but fails to address how the parameters interact with the described endpoint, what the output entails beyond a link, or any prerequisites. For a tool named 'Custom OAuth' with generic parameters, more context is needed to guide proper usage.

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 (e.g., method, path, body). The description does not add any parameter-specific semantics beyond what the schema provides; it only mentions the endpoint's purpose without explaining how parameters like 'method' or 'path' relate to the described functionality. Baseline 3 is appropriate as the schema handles parameter documentation, but the description does not compensate with additional context.

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 'This endpoint returns a stripe checkout session link to add balance to a user's wallet', which specifies a verb ('returns') and resource ('stripe checkout session link'), but the tool name and title ('Custom OAuth') are completely unrelated to payments/wallet functionality, creating confusion. It does not distinguish from siblings, as many tools handle payments (e.g., 'add_billing_details_13490005e0'), and the mismatch with the name/title makes it tautological in a misleading way.

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 a specific endpoint for adding wallet balance but does not explain why this tool is named 'Custom OAuth' or how it relates to OAuth functionality, nor does it reference any sibling tools for context. Usage is implied only for the described endpoint, with no exclusions or alternatives stated.

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