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. While it indicates this is a read operation ('List'), it doesn't mention important behavioral aspects like whether this requires authentication, what format the results are returned in, potential rate limits, or whether it's a complete list versus paginated results. The description provides basic functionality but lacks operational context.

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 sentences that efficiently communicate the core functionality and parameter usage. Every word earns its place, and the information is front-loaded with the main purpose stated first followed by parameter guidance.

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 simple read operation with one optional parameter and no output schema, the description provides adequate basic information about what the tool does. However, it lacks details about return format, authentication requirements, and error conditions that would be helpful for an agent. The description is minimally viable but has clear gaps in operational context.

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?

The description mentions the 'account_id' parameter and explains its purpose ('to target a specific mailbox'), which adds semantic meaning beyond the schema's description ('List folders for specific account'). However, with 100% schema description coverage for the single parameter, the description only provides marginal additional value. The baseline of 3 is appropriate when the schema already documents parameters adequately.

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 ('all email folders/labels in the account') with specific technology context ('IMAP'). It distinguishes from obvious siblings like 'list_accounts' and 'list_emails' by focusing on folders/labels, but doesn't explicitly differentiate from 'list_unread_folders' which is a more specialized variant.

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 implied usage context by mentioning the optional 'account_id' parameter to target a specific mailbox, suggesting this tool can be used for both general listing and targeted operations. However, it doesn't explicitly state when to use this versus alternatives like 'list_unread_folders' or provide any exclusion criteria.

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