Inbound Email MCP Server

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

Annotations already declare readOnlyHint=false, destructiveHint=false, and idempotentHint=false, so the agent knows this is a non-destructive, non-idempotent write operation. The description adds useful context about the automatic 'from' address setting and support for HTML/text content, CC/BCC, and scheduled sending, but doesn't disclose rate limits, authentication requirements, or error behavior beyond what annotations provide.

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 perfectly concise with two sentences that are front-loaded with the core purpose and then list key features. Every sentence earns its place by providing essential information without redundancy or unnecessary elaboration.

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 write operation tool with no output schema, the description provides good context about the automatic 'from' address and supported features. However, it doesn't explain what happens after sending (success/failure responses, delivery confirmation) or potential limitations. Given the complexity of email sending and lack of output schema, some additional behavioral context would be helpful.

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?

With 100% schema description coverage, the input schema already documents all 8 parameters thoroughly. The description mentions support for HTML/text content, CC/BCC, and scheduled sending, which aligns with parameters but doesn't add significant meaning beyond what the schema provides. The baseline of 3 is appropriate when 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 clearly states the specific action ('send an email'), identifies the resource ('from your agent mailbox'), and distinguishes it from siblings like 'send_email' by specifying the 'from' address is automatically set to the mailbox address via x-inbound-mailbox header. This provides precise differentiation from other email-sending 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 provides clear context about when to use this tool (sending from the agent mailbox with automatic 'from' address setting) but doesn't explicitly mention when NOT to use it or name specific alternatives like 'send_email'. It implies usage for mailbox-based sending but lacks explicit exclusion guidance.

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