MCP Email Service

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

With no annotations provided, the description carries the full burden. It discloses that the tool fetches headers without downloading the body (clarifying scope) and mentions the account_id recommendation for accurate mailbox targeting. However, it lacks details on permissions needed, rate limits, error conditions, or what the return format looks like (e.g., JSON structure).

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 two sentences, front-loaded with the core purpose and followed by a practical tip. Every word earns its place, with no redundancy or fluff, making it highly efficient and easy to parse.

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 no annotations and no output schema, the description adequately covers the tool's purpose and basic usage but lacks details on behavioral aspects like authentication, error handling, or return format. For a read operation with 4 parameters, it provides enough to get started but leaves gaps in full operational understanding.

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 parameters thoroughly. The description adds marginal value by implying that account_id helps with 'UID lookup' accuracy, but it does not provide additional syntax, format, or usage details beyond what the schema specifies. Baseline 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 ('Fetch only email headers') and resource ('email headers'), distinguishing it from siblings like get_email_detail (which presumably downloads full content) and get_email_attachments. It explicitly mentions what is excluded ('without downloading the body'), making the purpose unambiguous.

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 for when to use this tool ('Fetch only email headers... without downloading the body') and includes a practical recommendation ('account_id recommended so the UID lookup hits the right mailbox'). However, it does not explicitly state when NOT to use it or name specific alternatives among the siblings (e.g., get_email_detail for full content).

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