MCP Email Service

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

With no annotations provided, the description carries full burden for behavioral disclosure. 'List emails from inbox' implies a read-only operation, but doesn't specify whether this requires authentication, what format the results come in (IDs, summaries, or full emails), whether it supports pagination beyond the limit parameter, or any rate limits. The description is minimal and leaves critical behavioral aspects unspecified.

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 - just four words that directly state the tool's function. There's zero wasted language, and it's perfectly front-loaded with the essential information. Every word earns its place in this minimal but complete statement of purpose.

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 3 parameters, no annotations, and no output schema, the description is inadequate. It doesn't explain what the tool returns (email IDs, subjects, snippets, or full emails), doesn't mention authentication requirements, and provides no context about the email system being accessed. Given the complexity of email systems and the lack of structured documentation, the description should do much more.

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 all parameters are documented in the schema. The description adds no additional parameter information beyond what's in the schema - it doesn't explain parameter interactions, default behaviors, or provide usage examples. This meets the baseline for high schema coverage but doesn't enhance understanding.

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 verb ('list') and resource ('emails from inbox'), making the purpose immediately understandable. It distinguishes itself from siblings like get_email_detail (which retrieves specific email content) and get_unread_count (which only counts). However, it doesn't explicitly differentiate from batch operations or specify that it retrieves metadata rather than full content.

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 when to choose list_emails over get_email_detail for viewing content, or when to use it versus batch operations for multiple emails. There's no context about prerequisites, limitations, or typical use cases.

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